xref: /titanic_41/usr/src/uts/common/os/kmem.c (revision dfac3eb25a53097b94643fa6f32bb2fc1107df0c)

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/*
 * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*
 * Kernel memory allocator, as described in the following two papers and a
 * statement about the consolidator:
 *
 * Jeff Bonwick,
 * The Slab Allocator: An Object-Caching Kernel Memory Allocator.
 * Proceedings of the Summer 1994 Usenix Conference.
 * Available as /shared/sac/PSARC/1994/028/materials/kmem.pdf.
 *
 * Jeff Bonwick and Jonathan Adams,
 * Magazines and vmem: Extending the Slab Allocator to Many CPUs and
 * Arbitrary Resources.
 * Proceedings of the 2001 Usenix Conference.
 * Available as /shared/sac/PSARC/2000/550/materials/vmem.pdf.
 *
 * kmem Slab Consolidator Big Theory Statement:
 *
 * 1. Motivation
 *
 * As stated in Bonwick94, slabs provide the following advantages over other
 * allocation structures in terms of memory fragmentation:
 *
 *  - Internal fragmentation (per-buffer wasted space) is minimal.
 *  - Severe external fragmentation (unused buffers on the free list) is
 *    unlikely.
 *
 * Segregating objects by size eliminates one source of external fragmentation,
 * and according to Bonwick:
 *
 *   The other reason that slabs reduce external fragmentation is that all
 *   objects in a slab are of the same type, so they have the same lifetime
 *   distribution. The resulting segregation of short-lived and long-lived
 *   objects at slab granularity reduces the likelihood of an entire page being
 *   held hostage due to a single long-lived allocation [Barrett93, Hanson90].
 *
 * While unlikely, severe external fragmentation remains possible. Clients that
 * allocate both short- and long-lived objects from the same cache cannot
 * anticipate the distribution of long-lived objects within the allocator's slab
 * implementation. Even a small percentage of long-lived objects distributed
 * randomly across many slabs can lead to a worst case scenario where the client
 * frees the majority of its objects and the system gets back almost none of the
 * slabs. Despite the client doing what it reasonably can to help the system
 * reclaim memory, the allocator cannot shake free enough slabs because of
 * lonely allocations stubbornly hanging on. Although the allocator is in a
 * position to diagnose the fragmentation, there is nothing that the allocator
 * by itself can do about it. It only takes a single allocated object to prevent
 * an entire slab from being reclaimed, and any object handed out by
 * kmem_cache_alloc() is by definition in the client's control. Conversely,
 * although the client is in a position to move a long-lived object, it has no
 * way of knowing if the object is causing fragmentation, and if so, where to
 * move it. A solution necessarily requires further cooperation between the
 * allocator and the client.
 *
 * 2. Move Callback
 *
 * The kmem slab consolidator therefore adds a move callback to the
 * allocator/client interface, improving worst-case external fragmentation in
 * kmem caches that supply a function to move objects from one memory location
 * to another. In a situation of low memory kmem attempts to consolidate all of
 * a cache's slabs at once; otherwise it works slowly to bring external
 * fragmentation within the 1/8 limit guaranteed for internal fragmentation,
 * thereby helping to avoid a low memory situation in the future.
 *
 * The callback has the following signature:
 *
 *   kmem_cbrc_t move(void *old, void *new, size_t size, void *user_arg)
 *
 * It supplies the kmem client with two addresses: the allocated object that
 * kmem wants to move and a buffer selected by kmem for the client to use as the
 * copy destination. The callback is kmem's way of saying "Please get off of
 * this buffer and use this one instead." kmem knows where it wants to move the
 * object in order to best reduce fragmentation. All the client needs to know
 * about the second argument (void *new) is that it is an allocated, constructed
 * object ready to take the contents of the old object. When the move function
 * is called, the system is likely to be low on memory, and the new object
 * spares the client from having to worry about allocating memory for the
 * requested move. The third argument supplies the size of the object, in case a
 * single move function handles multiple caches whose objects differ only in
 * size (such as zio_buf_512, zio_buf_1024, etc). Finally, the same optional
 * user argument passed to the constructor, destructor, and reclaim functions is
 * also passed to the move callback.
 *
 * 2.1 Setting the Move Callback
 *
 * The client sets the move callback after creating the cache and before
 * allocating from it:
 *
 *	object_cache = kmem_cache_create(...);
 *      kmem_cache_set_move(object_cache, object_move);
 *
 * 2.2 Move Callback Return Values
 *
 * Only the client knows about its own data and when is a good time to move it.
 * The client is cooperating with kmem to return unused memory to the system,
 * and kmem respectfully accepts this help at the client's convenience. When
 * asked to move an object, the client can respond with any of the following:
 *
 *   typedef enum kmem_cbrc {
 *           KMEM_CBRC_YES,
 *           KMEM_CBRC_NO,
 *           KMEM_CBRC_LATER,
 *           KMEM_CBRC_DONT_NEED,
 *           KMEM_CBRC_DONT_KNOW
 *   } kmem_cbrc_t;
 *
 * The client must not explicitly kmem_cache_free() either of the objects passed
 * to the callback, since kmem wants to free them directly to the slab layer
 * (bypassing the per-CPU magazine layer). The response tells kmem which of the
 * objects to free:
 *
 *       YES: (Did it) The client moved the object, so kmem frees the old one.
 *        NO: (Never) The client refused, so kmem frees the new object (the
 *            unused copy destination). kmem also marks the slab of the old
 *            object so as not to bother the client with further callbacks for
 *            that object as long as the slab remains on the partial slab list.
 *            (The system won't be getting the slab back as long as the
 *            immovable object holds it hostage, so there's no point in moving
 *            any of its objects.)
 *     LATER: The client is using the object and cannot move it now, so kmem
 *            frees the new object (the unused copy destination). kmem still
 *            attempts to move other objects off the slab, since it expects to
 *            succeed in clearing the slab in a later callback. The client
 *            should use LATER instead of NO if the object is likely to become
 *            movable very soon.
 * DONT_NEED: The client no longer needs the object, so kmem frees the old along
 *            with the new object (the unused copy destination). This response
 *            is the client's opportunity to be a model citizen and give back as
 *            much as it can.
 * DONT_KNOW: The client does not know about the object because
 *            a) the client has just allocated the object and not yet put it
 *               wherever it expects to find known objects
 *            b) the client has removed the object from wherever it expects to
 *               find known objects and is about to free it, or
 *            c) the client has freed the object.
 *            In all these cases (a, b, and c) kmem frees the new object (the
 *            unused copy destination) and searches for the old object in the
 *            magazine layer. If found, the object is removed from the magazine
 *            layer and freed to the slab layer so it will no longer hold the
 *            slab hostage.
 *
 * 2.3 Object States
 *
 * Neither kmem nor the client can be assumed to know the object's whereabouts
 * at the time of the callback. An object belonging to a kmem cache may be in
 * any of the following states:
 *
 * 1. Uninitialized on the slab
 * 2. Allocated from the slab but not constructed (still uninitialized)
 * 3. Allocated from the slab, constructed, but not yet ready for business
 *    (not in a valid state for the move callback)
 * 4. In use (valid and known to the client)
 * 5. About to be freed (no longer in a valid state for the move callback)
 * 6. Freed to a magazine (still constructed)
 * 7. Allocated from a magazine, not yet ready for business (not in a valid
 *    state for the move callback), and about to return to state #4
 * 8. Deconstructed on a magazine that is about to be freed
 * 9. Freed to the slab
 *
 * Since the move callback may be called at any time while the object is in any
 * of the above states (except state #1), the client needs a safe way to
 * determine whether or not it knows about the object. Specifically, the client
 * needs to know whether or not the object is in state #4, the only state in
 * which a move is valid. If the object is in any other state, the client should
 * immediately return KMEM_CBRC_DONT_KNOW, since it is unsafe to access any of
 * the object's fields.
 *
 * Note that although an object may be in state #4 when kmem initiates the move
 * request, the object may no longer be in that state by the time kmem actually
 * calls the move function. Not only does the client free objects
 * asynchronously, kmem itself puts move requests on a queue where thay are
 * pending until kmem processes them from another context. Also, objects freed
 * to a magazine appear allocated from the point of view of the slab layer, so
 * kmem may even initiate requests for objects in a state other than state #4.
 *
 * 2.3.1 Magazine Layer
 *
 * An important insight revealed by the states listed above is that the magazine
 * layer is populated only by kmem_cache_free(). Magazines of constructed
 * objects are never populated directly from the slab layer (which contains raw,
 * unconstructed objects). Whenever an allocation request cannot be satisfied
 * from the magazine layer, the magazines are bypassed and the request is
 * satisfied from the slab layer (creating a new slab if necessary). kmem calls
 * the object constructor only when allocating from the slab layer, and only in
 * response to kmem_cache_alloc() or to prepare the destination buffer passed in
 * the move callback. kmem does not preconstruct objects in anticipation of
 * kmem_cache_alloc().
 *
 * 2.3.2 Object Constructor and Destructor
 *
 * If the client supplies a destructor, it must be valid to call the destructor
 * on a newly created object (immediately after the constructor).
 *
 * 2.4 Recognizing Known Objects
 *
 * There is a simple test to determine safely whether or not the client knows
 * about a given object in the move callback. It relies on the fact that kmem
 * guarantees that the object of the move callback has only been touched by the
 * client itself or else by kmem. kmem does this by ensuring that none of the
 * cache's slabs are freed to the virtual memory (VM) subsystem while a move
 * callback is pending. When the last object on a slab is freed, if there is a
 * pending move, kmem puts the slab on a per-cache dead list and defers freeing
 * slabs on that list until all pending callbacks are completed. That way,
 * clients can be certain that the object of a move callback is in one of the
 * states listed above, making it possible to distinguish known objects (in
 * state #4) using the two low order bits of any pointer member (with the
 * exception of 'char *' or 'short *' which may not be 4-byte aligned on some
 * platforms).
 *
 * The test works as long as the client always transitions objects from state #4
 * (known, in use) to state #5 (about to be freed, invalid) by setting the low
 * order bit of the client-designated pointer member. Since kmem only writes
 * invalid memory patterns, such as 0xbaddcafe to uninitialized memory and
 * 0xdeadbeef to freed memory, any scribbling on the object done by kmem is
 * guaranteed to set at least one of the two low order bits. Therefore, given an
 * object with a back pointer to a 'container_t *o_container', the client can
 * test
 *
 *      container_t *container = object->o_container;
 *      if ((uintptr_t)container & 0x3) {
 *              return (KMEM_CBRC_DONT_KNOW);
 *      }
 *
 * Typically, an object will have a pointer to some structure with a list or
 * hash where objects from the cache are kept while in use. Assuming that the
 * client has some way of knowing that the container structure is valid and will
 * not go away during the move, and assuming that the structure includes a lock
 * to protect whatever collection is used, then the client would continue as
 * follows:
 *
 *	// Ensure that the container structure does not go away.
 *      if (container_hold(container) == 0) {
 *              return (KMEM_CBRC_DONT_KNOW);
 *      }
 *      mutex_enter(&container->c_objects_lock);
 *      if (container != object->o_container) {
 *              mutex_exit(&container->c_objects_lock);
 *              container_rele(container);
 *              return (KMEM_CBRC_DONT_KNOW);
 *      }
 *
 * At this point the client knows that the object cannot be freed as long as
 * c_objects_lock is held. Note that after acquiring the lock, the client must
 * recheck the o_container pointer in case the object was removed just before
 * acquiring the lock.
 *
 * When the client is about to free an object, it must first remove that object
 * from the list, hash, or other structure where it is kept. At that time, to
 * mark the object so it can be distinguished from the remaining, known objects,
 * the client sets the designated low order bit:
 *
 *      mutex_enter(&container->c_objects_lock);
 *      object->o_container = (void *)((uintptr_t)object->o_container | 0x1);
 *      list_remove(&container->c_objects, object);
 *      mutex_exit(&container->c_objects_lock);
 *
 * In the common case, the object is freed to the magazine layer, where it may
 * be reused on a subsequent allocation without the overhead of calling the
 * constructor. While in the magazine it appears allocated from the point of
 * view of the slab layer, making it a candidate for the move callback. Most
 * objects unrecognized by the client in the move callback fall into this
 * category and are cheaply distinguished from known objects by the test
 * described earlier. Since recognition is cheap for the client, and searching
 * magazines is expensive for kmem, kmem defers searching until the client first
 * returns KMEM_CBRC_DONT_KNOW. As long as the needed effort is reasonable, kmem
 * elsewhere does what it can to avoid bothering the client unnecessarily.
 *
 * Invalidating the designated pointer member before freeing the object marks
 * the object to be avoided in the callback, and conversely, assigning a valid
 * value to the designated pointer member after allocating the object makes the
 * object fair game for the callback:
 *
 *      ... allocate object ...
 *      ... set any initial state not set by the constructor ...
 *
 *      mutex_enter(&container->c_objects_lock);
 *      list_insert_tail(&container->c_objects, object);
 *      membar_producer();
 *      object->o_container = container;
 *      mutex_exit(&container->c_objects_lock);
 *
 * Note that everything else must be valid before setting o_container makes the
 * object fair game for the move callback. The membar_producer() call ensures
 * that all the object's state is written to memory before setting the pointer
 * that transitions the object from state #3 or #7 (allocated, constructed, not
 * yet in use) to state #4 (in use, valid). That's important because the move
 * function has to check the validity of the pointer before it can safely
 * acquire the lock protecting the collection where it expects to find known
 * objects.
 *
 * This method of distinguishing known objects observes the usual symmetry:
 * invalidating the designated pointer is the first thing the client does before
 * freeing the object, and setting the designated pointer is the last thing the
 * client does after allocating the object. Of course, the client is not
 * required to use this method. Fundamentally, how the client recognizes known
 * objects is completely up to the client, but this method is recommended as an
 * efficient and safe way to take advantage of the guarantees made by kmem. If
 * the entire object is arbitrary data without any markable bits from a suitable
 * pointer member, then the client must find some other method, such as
 * searching a hash table of known objects.
 *
 * 2.5 Preventing Objects From Moving
 *
 * Besides a way to distinguish known objects, the other thing that the client
 * needs is a strategy to ensure that an object will not move while the client
 * is actively using it. The details of satisfying this requirement tend to be
 * highly cache-specific. It might seem that the same rules that let a client
 * remove an object safely should also decide when an object can be moved
 * safely. However, any object state that makes a removal attempt invalid is
 * likely to be long-lasting for objects that the client does not expect to
 * remove. kmem knows nothing about the object state and is equally likely (from
 * the client's point of view) to request a move for any object in the cache,
 * whether prepared for removal or not. Even a low percentage of objects stuck
 * in place by unremovability will defeat the consolidator if the stuck objects
 * are the same long-lived allocations likely to hold slabs hostage.
 * Fundamentally, the consolidator is not aimed at common cases. Severe external
 * fragmentation is a worst case scenario manifested as sparsely allocated
 * slabs, by definition a low percentage of the cache's objects. When deciding
 * what makes an object movable, keep in mind the goal of the consolidator: to
 * bring worst-case external fragmentation within the limits guaranteed for
 * internal fragmentation. Removability is a poor criterion if it is likely to
 * exclude more than an insignificant percentage of objects for long periods of
 * time.
 *
 * A tricky general solution exists, and it has the advantage of letting you
 * move any object at almost any moment, practically eliminating the likelihood
 * that an object can hold a slab hostage. However, if there is a cache-specific
 * way to ensure that an object is not actively in use in the vast majority of
 * cases, a simpler solution that leverages this cache-specific knowledge is
 * preferred.
 *
 * 2.5.1 Cache-Specific Solution
 *
 * As an example of a cache-specific solution, the ZFS znode cache takes
 * advantage of the fact that the vast majority of znodes are only being
 * referenced from the DNLC. (A typical case might be a few hundred in active
 * use and a hundred thousand in the DNLC.) In the move callback, after the ZFS
 * client has established that it recognizes the znode and can access its fields
 * safely (using the method described earlier), it then tests whether the znode
 * is referenced by anything other than the DNLC. If so, it assumes that the
 * znode may be in active use and is unsafe to move, so it drops its locks and
 * returns KMEM_CBRC_LATER. The advantage of this strategy is that everywhere
 * else znodes are used, no change is needed to protect against the possibility
 * of the znode moving. The disadvantage is that it remains possible for an
 * application to hold a znode slab hostage with an open file descriptor.
 * However, this case ought to be rare and the consolidator has a way to deal
 * with it: If the client responds KMEM_CBRC_LATER repeatedly for the same
 * object, kmem eventually stops believing it and treats the slab as if the
 * client had responded KMEM_CBRC_NO. Having marked the hostage slab, kmem can
 * then focus on getting it off of the partial slab list by allocating rather
 * than freeing all of its objects. (Either way of getting a slab off the
 * free list reduces fragmentation.)
 *
 * 2.5.2 General Solution
 *
 * The general solution, on the other hand, requires an explicit hold everywhere
 * the object is used to prevent it from moving. To keep the client locking
 * strategy as uncomplicated as possible, kmem guarantees the simplifying
 * assumption that move callbacks are sequential, even across multiple caches.
 * Internally, a global queue processed by a single thread supports all caches
 * implementing the callback function. No matter how many caches supply a move
 * function, the consolidator never moves more than one object at a time, so the
 * client does not have to worry about tricky lock ordering involving several
 * related objects from different kmem caches.
 *
 * The general solution implements the explicit hold as a read-write lock, which
 * allows multiple readers to access an object from the cache simultaneously
 * while a single writer is excluded from moving it. A single rwlock for the
 * entire cache would lock out all threads from using any of the cache's objects
 * even though only a single object is being moved, so to reduce contention,
 * the client can fan out the single rwlock into an array of rwlocks hashed by
 * the object address, making it probable that moving one object will not
 * prevent other threads from using a different object. The rwlock cannot be a
 * member of the object itself, because the possibility of the object moving
 * makes it unsafe to access any of the object's fields until the lock is
 * acquired.
 *
 * Assuming a small, fixed number of locks, it's possible that multiple objects
 * will hash to the same lock. A thread that needs to use multiple objects in
 * the same function may acquire the same lock multiple times. Since rwlocks are
 * reentrant for readers, and since there is never more than a single writer at
 * a time (assuming that the client acquires the lock as a writer only when
 * moving an object inside the callback), there would seem to be no problem.
 * However, a client locking multiple objects in the same function must handle
 * one case of potential deadlock: Assume that thread A needs to prevent both
 * object 1 and object 2 from moving, and thread B, the callback, meanwhile
 * tries to move object 3. It's possible, if objects 1, 2, and 3 all hash to the
 * same lock, that thread A will acquire the lock for object 1 as a reader
 * before thread B sets the lock's write-wanted bit, preventing thread A from
 * reacquiring the lock for object 2 as a reader. Unable to make forward
 * progress, thread A will never release the lock for object 1, resulting in
 * deadlock.
 *
 * There are two ways of avoiding the deadlock just described. The first is to
 * use rw_tryenter() rather than rw_enter() in the callback function when
 * attempting to acquire the lock as a writer. If tryenter discovers that the
 * same object (or another object hashed to the same lock) is already in use, it
 * aborts the callback and returns KMEM_CBRC_LATER. The second way is to use
 * rprwlock_t (declared in common/fs/zfs/sys/rprwlock.h) instead of rwlock_t,
 * since it allows a thread to acquire the lock as a reader in spite of a
 * waiting writer. This second approach insists on moving the object now, no
 * matter how many readers the move function must wait for in order to do so,
 * and could delay the completion of the callback indefinitely (blocking
 * callbacks to other clients). In practice, a less insistent callback using
 * rw_tryenter() returns KMEM_CBRC_LATER infrequently enough that there seems
 * little reason to use anything else.
 *
 * Avoiding deadlock is not the only problem that an implementation using an
 * explicit hold needs to solve. Locking the object in the first place (to
 * prevent it from moving) remains a problem, since the object could move
 * between the time you obtain a pointer to the object and the time you acquire
 * the rwlock hashed to that pointer value. Therefore the client needs to
 * recheck the value of the pointer after acquiring the lock, drop the lock if
 * the value has changed, and try again. This requires a level of indirection:
 * something that points to the object rather than the object itself, that the
 * client can access safely while attempting to acquire the lock. (The object
 * itself cannot be referenced safely because it can move at any time.)
 * The following lock-acquisition function takes whatever is safe to reference
 * (arg), follows its pointer to the object (using function f), and tries as
 * often as necessary to acquire the hashed lock and verify that the object
 * still has not moved:
 *
 *      object_t *
 *      object_hold(object_f f, void *arg)
 *      {
 *              object_t *op;
 *
 *              op = f(arg);
 *              if (op == NULL) {
 *                      return (NULL);
 *              }
 *
 *              rw_enter(OBJECT_RWLOCK(op), RW_READER);
 *              while (op != f(arg)) {
 *                      rw_exit(OBJECT_RWLOCK(op));
 *                      op = f(arg);
 *                      if (op == NULL) {
 *                              break;
 *                      }
 *                      rw_enter(OBJECT_RWLOCK(op), RW_READER);
 *              }
 *
 *              return (op);
 *      }
 *
 * The OBJECT_RWLOCK macro hashes the object address to obtain the rwlock. The
 * lock reacquisition loop, while necessary, almost never executes. The function
 * pointer f (used to obtain the object pointer from arg) has the following type
 * definition:
 *
 *      typedef object_t *(*object_f)(void *arg);
 *
 * An object_f implementation is likely to be as simple as accessing a structure
 * member:
 *
 *      object_t *
 *      s_object(void *arg)
 *      {
 *              something_t *sp = arg;
 *              return (sp->s_object);
 *      }
 *
 * The flexibility of a function pointer allows the path to the object to be
 * arbitrarily complex and also supports the notion that depending on where you
 * are using the object, you may need to get it from someplace different.
 *
 * The function that releases the explicit hold is simpler because it does not
 * have to worry about the object moving:
 *
 *      void
 *      object_rele(object_t *op)
 *      {
 *              rw_exit(OBJECT_RWLOCK(op));
 *      }
 *
 * The caller is spared these details so that obtaining and releasing an
 * explicit hold feels like a simple mutex_enter()/mutex_exit() pair. The caller
 * of object_hold() only needs to know that the returned object pointer is valid
 * if not NULL and that the object will not move until released.
 *
 * Although object_hold() prevents an object from moving, it does not prevent it
 * from being freed. The caller must take measures before calling object_hold()
 * (afterwards is too late) to ensure that the held object cannot be freed. The
 * caller must do so without accessing the unsafe object reference, so any lock
 * or reference count used to ensure the continued existence of the object must
 * live outside the object itself.
 *
 * Obtaining a new object is a special case where an explicit hold is impossible
 * for the caller. Any function that returns a newly allocated object (either as
 * a return value, or as an in-out paramter) must return it already held; after
 * the caller gets it is too late, since the object cannot be safely accessed
 * without the level of indirection described earlier. The following
 * object_alloc() example uses the same code shown earlier to transition a new
 * object into the state of being recognized (by the client) as a known object.
 * The function must acquire the hold (rw_enter) before that state transition
 * makes the object movable:
 *
 *      static object_t *
 *      object_alloc(container_t *container)
 *      {
 *              object_t *object = kmem_cache_alloc(object_cache, 0);
 *              ... set any initial state not set by the constructor ...
 *              rw_enter(OBJECT_RWLOCK(object), RW_READER);
 *              mutex_enter(&container->c_objects_lock);
 *              list_insert_tail(&container->c_objects, object);
 *              membar_producer();
 *              object->o_container = container;
 *              mutex_exit(&container->c_objects_lock);
 *              return (object);
 *      }
 *
 * Functions that implicitly acquire an object hold (any function that calls
 * object_alloc() to supply an object for the caller) need to be carefully noted
 * so that the matching object_rele() is not neglected. Otherwise, leaked holds
 * prevent all objects hashed to the affected rwlocks from ever being moved.
 *
 * The pointer to a held object can be hashed to the holding rwlock even after
 * the object has been freed. Although it is possible to release the hold
 * after freeing the object, you may decide to release the hold implicitly in
 * whatever function frees the object, so as to release the hold as soon as
 * possible, and for the sake of symmetry with the function that implicitly
 * acquires the hold when it allocates the object. Here, object_free() releases
 * the hold acquired by object_alloc(). Its implicit object_rele() forms a
 * matching pair with object_hold():
 *
 *      void
 *      object_free(object_t *object)
 *      {
 *              container_t *container;
 *
 *              ASSERT(object_held(object));
 *              container = object->o_container;
 *              mutex_enter(&container->c_objects_lock);
 *              object->o_container =
 *                  (void *)((uintptr_t)object->o_container | 0x1);
 *              list_remove(&container->c_objects, object);
 *              mutex_exit(&container->c_objects_lock);
 *              object_rele(object);
 *              kmem_cache_free(object_cache, object);
 *      }
 *
 * Note that object_free() cannot safely accept an object pointer as an argument
 * unless the object is already held. Any function that calls object_free()
 * needs to be carefully noted since it similarly forms a matching pair with
 * object_hold().
 *
 * To complete the picture, the following callback function implements the
 * general solution by moving objects only if they are currently unheld:
 *
 *      static kmem_cbrc_t
 *      object_move(void *buf, void *newbuf, size_t size, void *arg)
 *      {
 *              object_t *op = buf, *np = newbuf;
 *              container_t *container;
 *
 *              container = op->o_container;
 *              if ((uintptr_t)container & 0x3) {
 *                      return (KMEM_CBRC_DONT_KNOW);
 *              }
 *
 *	        // Ensure that the container structure does not go away.
 *              if (container_hold(container) == 0) {
 *                      return (KMEM_CBRC_DONT_KNOW);
 *              }
 *
 *              mutex_enter(&container->c_objects_lock);
 *              if (container != op->o_container) {
 *                      mutex_exit(&container->c_objects_lock);
 *                      container_rele(container);
 *                      return (KMEM_CBRC_DONT_KNOW);
 *              }
 *
 *              if (rw_tryenter(OBJECT_RWLOCK(op), RW_WRITER) == 0) {
 *                      mutex_exit(&container->c_objects_lock);
 *                      container_rele(container);
 *                      return (KMEM_CBRC_LATER);
 *              }
 *
 *              object_move_impl(op, np); // critical section
 *              rw_exit(OBJECT_RWLOCK(op));
 *
 *              op->o_container = (void *)((uintptr_t)op->o_container | 0x1);
 *              list_link_replace(&op->o_link_node, &np->o_link_node);
 *              mutex_exit(&container->c_objects_lock);
 *              container_rele(container);
 *              return (KMEM_CBRC_YES);
 *      }
 *
 * Note that object_move() must invalidate the designated o_container pointer of
 * the old object in the same way that object_free() does, since kmem will free
 * the object in response to the KMEM_CBRC_YES return value.
 *
 * The lock order in object_move() differs from object_alloc(), which locks
 * OBJECT_RWLOCK first and &container->c_objects_lock second, but as long as the
 * callback uses rw_tryenter() (preventing the deadlock described earlier), it's
 * not a problem. Holding the lock on the object list in the example above
 * through the entire callback not only prevents the object from going away, it
 * also allows you to lock the list elsewhere and know that none of its elements
 * will move during iteration.
 *
 * Adding an explicit hold everywhere an object from the cache is used is tricky
 * and involves much more change to client code than a cache-specific solution
 * that leverages existing state to decide whether or not an object is
 * movable. However, this approach has the advantage that no object remains
 * immovable for any significant length of time, making it extremely unlikely
 * that long-lived allocations can continue holding slabs hostage; and it works
 * for any cache.
 *
 * 3. Consolidator Implementation
 *
 * Once the client supplies a move function that a) recognizes known objects and
 * b) avoids moving objects that are actively in use, the remaining work is up
 * to the consolidator to decide which objects to move and when to issue
 * callbacks.
 *
 * The consolidator relies on the fact that a cache's slabs are ordered by
 * usage. Each slab has a fixed number of objects. Depending on the slab's
 * "color" (the offset of the first object from the beginning of the slab;
 * offsets are staggered to mitigate false sharing of cache lines) it is either
 * the maximum number of objects per slab determined at cache creation time or
 * else the number closest to the maximum that fits within the space remaining
 * after the initial offset. A completely allocated slab may contribute some
 * internal fragmentation (per-slab overhead) but no external fragmentation, so
 * it is of no interest to the consolidator. At the other extreme, slabs whose
 * objects have all been freed to the slab are released to the virtual memory
 * (VM) subsystem (objects freed to magazines are still allocated as far as the
 * slab is concerned). External fragmentation exists when there are slabs
 * somewhere between these extremes. A partial slab has at least one but not all
 * of its objects allocated. The more partial slabs, and the fewer allocated
 * objects on each of them, the higher the fragmentation. Hence the
 * consolidator's overall strategy is to reduce the number of partial slabs by
 * moving allocated objects from the least allocated slabs to the most allocated
 * slabs.
 *
 * Partial slabs are kept in an AVL tree ordered by usage. Completely allocated
 * slabs are kept separately in an unordered list. Since the majority of slabs
 * tend to be completely allocated (a typical unfragmented cache may have
 * thousands of complete slabs and only a single partial slab), separating
 * complete slabs improves the efficiency of partial slab ordering, since the
 * complete slabs do not affect the depth or balance of the AVL tree. This
 * ordered sequence of partial slabs acts as a "free list" supplying objects for
 * allocation requests.
 *
 * Objects are always allocated from the first partial slab in the free list,
 * where the allocation is most likely to eliminate a partial slab (by
 * completely allocating it). Conversely, when a single object from a completely
 * allocated slab is freed to the slab, that slab is added to the front of the
 * free list. Since most free list activity involves highly allocated slabs
 * coming and going at the front of the list, slabs tend naturally toward the
 * ideal order: highly allocated at the front, sparsely allocated at the back.
 * Slabs with few allocated objects are likely to become completely free if they
 * keep a safe distance away from the front of the free list. Slab misorders
 * interfere with the natural tendency of slabs to become completely free or
 * completely allocated. For example, a slab with a single allocated object
 * needs only a single free to escape the cache; its natural desire is
 * frustrated when it finds itself at the front of the list where a second
 * allocation happens just before the free could have released it. Another slab
 * with all but one object allocated might have supplied the buffer instead, so
 * that both (as opposed to neither) of the slabs would have been taken off the
 * free list.
 *
 * Although slabs tend naturally toward the ideal order, misorders allowed by a
 * simple list implementation defeat the consolidator's strategy of merging
 * least- and most-allocated slabs. Without an AVL tree to guarantee order, kmem
 * needs another way to fix misorders to optimize its callback strategy. One
 * approach is to periodically scan a limited number of slabs, advancing a
 * marker to hold the current scan position, and to move extreme misorders to
 * the front or back of the free list and to the front or back of the current
 * scan range. By making consecutive scan ranges overlap by one slab, the least
 * allocated slab in the current range can be carried along from the end of one
 * scan to the start of the next.
 *
 * Maintaining partial slabs in an AVL tree relieves kmem of this additional
 * task, however. Since most of the cache's activity is in the magazine layer,
 * and allocations from the slab layer represent only a startup cost, the
 * overhead of maintaining a balanced tree is not a significant concern compared
 * to the opportunity of reducing complexity by eliminating the partial slab
 * scanner just described. The overhead of an AVL tree is minimized by
 * maintaining only partial slabs in the tree and keeping completely allocated
 * slabs separately in a list. To avoid increasing the size of the slab
 * structure the AVL linkage pointers are reused for the slab's list linkage,
 * since the slab will always be either partial or complete, never stored both
 * ways at the same time. To further minimize the overhead of the AVL tree the
 * compare function that orders partial slabs by usage divides the range of
 * allocated object counts into bins such that counts within the same bin are
 * considered equal. Binning partial slabs makes it less likely that allocating
 * or freeing a single object will change the slab's order, requiring a tree
 * reinsertion (an avl_remove() followed by an avl_add(), both potentially
 * requiring some rebalancing of the tree). Allocation counts closest to
 * completely free and completely allocated are left unbinned (finely sorted) to
 * better support the consolidator's strategy of merging slabs at either
 * extreme.
 *
 * 3.1 Assessing Fragmentation and Selecting Candidate Slabs
 *
 * The consolidator piggybacks on the kmem maintenance thread and is called on
 * the same interval as kmem_cache_update(), once per cache every fifteen
 * seconds. kmem maintains a running count of unallocated objects in the slab
 * layer (cache_bufslab). The consolidator checks whether that number exceeds
 * 12.5% (1/8) of the total objects in the cache (cache_buftotal), and whether
 * there is a significant number of slabs in the cache (arbitrarily a minimum
 * 101 total slabs). Unused objects that have fallen out of the magazine layer's
 * working set are included in the assessment, and magazines in the depot are
 * reaped if those objects would lift cache_bufslab above the fragmentation
 * threshold. Once the consolidator decides that a cache is fragmented, it looks
 * for a candidate slab to reclaim, starting at the end of the partial slab free
 * list and scanning backwards. At first the consolidator is choosy: only a slab
 * with fewer than 12.5% (1/8) of its objects allocated qualifies (or else a
 * single allocated object, regardless of percentage). If there is difficulty
 * finding a candidate slab, kmem raises the allocation threshold incrementally,
 * up to a maximum 87.5% (7/8), so that eventually the consolidator will reduce
 * external fragmentation (unused objects on the free list) below 12.5% (1/8),
 * even in the worst case of every slab in the cache being almost 7/8 allocated.
 * The threshold can also be lowered incrementally when candidate slabs are easy
 * to find, and the threshold is reset to the minimum 1/8 as soon as the cache
 * is no longer fragmented.
 *
 * 3.2 Generating Callbacks
 *
 * Once an eligible slab is chosen, a callback is generated for every allocated
 * object on the slab, in the hope that the client will move everything off the
 * slab and make it reclaimable. Objects selected as move destinations are
 * chosen from slabs at the front of the free list. Assuming slabs in the ideal
 * order (most allocated at the front, least allocated at the back) and a
 * cooperative client, the consolidator will succeed in removing slabs from both
 * ends of the free list, completely allocating on the one hand and completely
 * freeing on the other. Objects selected as move destinations are allocated in
 * the kmem maintenance thread where move requests are enqueued. A separate
 * callback thread removes pending callbacks from the queue and calls the
 * client. The separate thread ensures that client code (the move function) does
 * not interfere with internal kmem maintenance tasks. A map of pending
 * callbacks keyed by object address (the object to be moved) is checked to
 * ensure that duplicate callbacks are not generated for the same object.
 * Allocating the move destination (the object to move to) prevents subsequent
 * callbacks from selecting the same destination as an earlier pending callback.
 *
 * Move requests can also be generated by kmem_cache_reap() when the system is
 * desperate for memory and by kmem_cache_move_notify(), called by the client to
 * notify kmem that a move refused earlier with KMEM_CBRC_LATER is now possible.
 * The map of pending callbacks is protected by the same lock that protects the
 * slab layer.
 *
 * When the system is desperate for memory, kmem does not bother to determine
 * whether or not the cache exceeds the fragmentation threshold, but tries to
 * consolidate as many slabs as possible. Normally, the consolidator chews
 * slowly, one sparsely allocated slab at a time during each maintenance
 * interval that the cache is fragmented. When desperate, the consolidator
 * starts at the last partial slab and enqueues callbacks for every allocated
 * object on every partial slab, working backwards until it reaches the first
 * partial slab. The first partial slab, meanwhile, advances in pace with the
 * consolidator as allocations to supply move destinations for the enqueued
 * callbacks use up the highly allocated slabs at the front of the free list.
 * Ideally, the overgrown free list collapses like an accordion, starting at
 * both ends and ending at the center with a single partial slab.
 *
 * 3.3 Client Responses
 *
 * When the client returns KMEM_CBRC_NO in response to the move callback, kmem
 * marks the slab that supplied the stuck object non-reclaimable and moves it to
 * front of the free list. The slab remains marked as long as it remains on the
 * free list, and it appears more allocated to the partial slab compare function
 * than any unmarked slab, no matter how many of its objects are allocated.
 * Since even one immovable object ties up the entire slab, the goal is to
 * completely allocate any slab that cannot be completely freed. kmem does not
 * bother generating callbacks to move objects from a marked slab unless the
 * system is desperate.
 *
 * When the client responds KMEM_CBRC_LATER, kmem increments a count for the
 * slab. If the client responds LATER too many times, kmem disbelieves and
 * treats the response as a NO. The count is cleared when the slab is taken off
 * the partial slab list or when the client moves one of the slab's objects.
 *
 * 4. Observability
 *
 * A kmem cache's external fragmentation is best observed with 'mdb -k' using
 * the ::kmem_slabs dcmd. For a complete description of the command, enter
 * '::help kmem_slabs' at the mdb prompt.
 */

#include <sys/kmem_impl.h>
#include <sys/vmem_impl.h>
#include <sys/param.h>
#include <sys/sysmacros.h>
#include <sys/vm.h>
#include <sys/proc.h>
#include <sys/tuneable.h>
#include <sys/systm.h>
#include <sys/cmn_err.h>
#include <sys/debug.h>
#include <sys/sdt.h>
#include <sys/mutex.h>
#include <sys/bitmap.h>
#include <sys/atomic.h>
#include <sys/kobj.h>
#include <sys/disp.h>
#include <vm/seg_kmem.h>
#include <sys/log.h>
#include <sys/callb.h>
#include <sys/taskq.h>
#include <sys/modctl.h>
#include <sys/reboot.h>
#include <sys/id32.h>
#include <sys/zone.h>
#include <sys/netstack.h>
#ifdef	DEBUG
#include <sys/random.h>
#endif

extern void streams_msg_init(void);
extern int segkp_fromheap;
extern void segkp_cache_free(void);

struct kmem_cache_kstat {
	kstat_named_t	kmc_buf_size;
	kstat_named_t	kmc_align;
	kstat_named_t	kmc_chunk_size;
	kstat_named_t	kmc_slab_size;
	kstat_named_t	kmc_alloc;
	kstat_named_t	kmc_alloc_fail;
	kstat_named_t	kmc_free;
	kstat_named_t	kmc_depot_alloc;
	kstat_named_t	kmc_depot_free;
	kstat_named_t	kmc_depot_contention;
	kstat_named_t	kmc_slab_alloc;
	kstat_named_t	kmc_slab_free;
	kstat_named_t	kmc_buf_constructed;
	kstat_named_t	kmc_buf_avail;
	kstat_named_t	kmc_buf_inuse;
	kstat_named_t	kmc_buf_total;
	kstat_named_t	kmc_buf_max;
	kstat_named_t	kmc_slab_create;
	kstat_named_t	kmc_slab_destroy;
	kstat_named_t	kmc_vmem_source;
	kstat_named_t	kmc_hash_size;
	kstat_named_t	kmc_hash_lookup_depth;
	kstat_named_t	kmc_hash_rescale;
	kstat_named_t	kmc_full_magazines;
	kstat_named_t	kmc_empty_magazines;
	kstat_named_t	kmc_magazine_size;
	kstat_named_t	kmc_move_callbacks;
	kstat_named_t	kmc_move_yes;
	kstat_named_t	kmc_move_no;
	kstat_named_t	kmc_move_later;
	kstat_named_t	kmc_move_dont_need;
	kstat_named_t	kmc_move_dont_know;
	kstat_named_t	kmc_move_hunt_found;
} kmem_cache_kstat = {
	{ "buf_size",		KSTAT_DATA_UINT64 },
	{ "align",		KSTAT_DATA_UINT64 },
	{ "chunk_size",		KSTAT_DATA_UINT64 },
	{ "slab_size",		KSTAT_DATA_UINT64 },
	{ "alloc",		KSTAT_DATA_UINT64 },
	{ "alloc_fail",		KSTAT_DATA_UINT64 },
	{ "free",		KSTAT_DATA_UINT64 },
	{ "depot_alloc",	KSTAT_DATA_UINT64 },
	{ "depot_free",		KSTAT_DATA_UINT64 },
	{ "depot_contention",	KSTAT_DATA_UINT64 },
	{ "slab_alloc",		KSTAT_DATA_UINT64 },
	{ "slab_free",		KSTAT_DATA_UINT64 },
	{ "buf_constructed",	KSTAT_DATA_UINT64 },
	{ "buf_avail",		KSTAT_DATA_UINT64 },
	{ "buf_inuse",		KSTAT_DATA_UINT64 },
	{ "buf_total",		KSTAT_DATA_UINT64 },
	{ "buf_max",		KSTAT_DATA_UINT64 },
	{ "slab_create",	KSTAT_DATA_UINT64 },
	{ "slab_destroy",	KSTAT_DATA_UINT64 },
	{ "vmem_source",	KSTAT_DATA_UINT64 },
	{ "hash_size",		KSTAT_DATA_UINT64 },
	{ "hash_lookup_depth",	KSTAT_DATA_UINT64 },
	{ "hash_rescale",	KSTAT_DATA_UINT64 },
	{ "full_magazines",	KSTAT_DATA_UINT64 },
	{ "empty_magazines",	KSTAT_DATA_UINT64 },
	{ "magazine_size",	KSTAT_DATA_UINT64 },
	{ "move_callbacks",	KSTAT_DATA_UINT64 },
	{ "move_yes",		KSTAT_DATA_UINT64 },
	{ "move_no",		KSTAT_DATA_UINT64 },
	{ "move_later",		KSTAT_DATA_UINT64 },
	{ "move_dont_need",	KSTAT_DATA_UINT64 },
	{ "move_dont_know",	KSTAT_DATA_UINT64 },
	{ "move_hunt_found",	KSTAT_DATA_UINT64 },
};

static kmutex_t kmem_cache_kstat_lock;

/*
 * The default set of caches to back kmem_alloc().
 * These sizes should be reevaluated periodically.
 *
 * We want allocations that are multiples of the coherency granularity
 * (64 bytes) to be satisfied from a cache which is a multiple of 64
 * bytes, so that it will be 64-byte aligned.  For all multiples of 64,
 * the next kmem_cache_size greater than or equal to it must be a
 * multiple of 64.
 */
static const int kmem_alloc_sizes[] = {
	1 * 8,
	2 * 8,
	3 * 8,
	4 * 8,		5 * 8,		6 * 8,		7 * 8,
	4 * 16,		5 * 16,		6 * 16,		7 * 16,
	4 * 32,		5 * 32,		6 * 32,		7 * 32,
	4 * 64,		5 * 64,		6 * 64,		7 * 64,
	4 * 128,	5 * 128,	6 * 128,	7 * 128,
	P2ALIGN(8192 / 7, 64),
	P2ALIGN(8192 / 6, 64),
	P2ALIGN(8192 / 5, 64),
	P2ALIGN(8192 / 4, 64),
	P2ALIGN(8192 / 3, 64),
	P2ALIGN(8192 / 2, 64),
	P2ALIGN(8192 / 1, 64),
	4096 * 3,
	8192 * 2,
	8192 * 3,
	8192 * 4,
};

#define	KMEM_MAXBUF	32768

static kmem_cache_t *kmem_alloc_table[KMEM_MAXBUF >> KMEM_ALIGN_SHIFT];

static kmem_magtype_t kmem_magtype[] = {
	{ 1,	8,	3200,	65536	},
	{ 3,	16,	256,	32768	},
	{ 7,	32,	64,	16384	},
	{ 15,	64,	0,	8192	},
	{ 31,	64,	0,	4096	},
	{ 47,	64,	0,	2048	},
	{ 63,	64,	0,	1024	},
	{ 95,	64,	0,	512	},
	{ 143,	64,	0,	0	},
};

static uint32_t kmem_reaping;
static uint32_t kmem_reaping_idspace;

/*
 * kmem tunables
 */
clock_t kmem_reap_interval;	/* cache reaping rate [15 * HZ ticks] */
int kmem_depot_contention = 3;	/* max failed tryenters per real interval */
pgcnt_t kmem_reapahead = 0;	/* start reaping N pages before pageout */
int kmem_panic = 1;		/* whether to panic on error */
int kmem_logging = 1;		/* kmem_log_enter() override */
uint32_t kmem_mtbf = 0;		/* mean time between failures [default: off] */
size_t kmem_transaction_log_size; /* transaction log size [2% of memory] */
size_t kmem_content_log_size;	/* content log size [2% of memory] */
size_t kmem_failure_log_size;	/* failure log [4 pages per CPU] */
size_t kmem_slab_log_size;	/* slab create log [4 pages per CPU] */
size_t kmem_content_maxsave = 256; /* KMF_CONTENTS max bytes to log */
size_t kmem_lite_minsize = 0;	/* minimum buffer size for KMF_LITE */
size_t kmem_lite_maxalign = 1024; /* maximum buffer alignment for KMF_LITE */
int kmem_lite_pcs = 4;		/* number of PCs to store in KMF_LITE mode */
size_t kmem_maxverify;		/* maximum bytes to inspect in debug routines */
size_t kmem_minfirewall;	/* hardware-enforced redzone threshold */

#ifdef DEBUG
int kmem_flags = KMF_AUDIT | KMF_DEADBEEF | KMF_REDZONE | KMF_CONTENTS;
#else
int kmem_flags = 0;
#endif
int kmem_ready;

static kmem_cache_t	*kmem_slab_cache;
static kmem_cache_t	*kmem_bufctl_cache;
static kmem_cache_t	*kmem_bufctl_audit_cache;

static kmutex_t		kmem_cache_lock;	/* inter-cache linkage only */
static list_t		kmem_caches;

static taskq_t		*kmem_taskq;
static kmutex_t		kmem_flags_lock;
static vmem_t		*kmem_metadata_arena;
static vmem_t		*kmem_msb_arena;	/* arena for metadata caches */
static vmem_t		*kmem_cache_arena;
static vmem_t		*kmem_hash_arena;
static vmem_t		*kmem_log_arena;
static vmem_t		*kmem_oversize_arena;
static vmem_t		*kmem_va_arena;
static vmem_t		*kmem_default_arena;
static vmem_t		*kmem_firewall_va_arena;
static vmem_t		*kmem_firewall_arena;

/*
 * Define KMEM_STATS to turn on statistic gathering. By default, it is only
 * turned on when DEBUG is also defined.
 */
#ifdef	DEBUG
#define	KMEM_STATS
#endif	/* DEBUG */

#ifdef	KMEM_STATS
#define	KMEM_STAT_ADD(stat)			((stat)++)
#define	KMEM_STAT_COND_ADD(cond, stat)		((void) (!(cond) || (stat)++))
#else
#define	KMEM_STAT_ADD(stat)			/* nothing */
#define	KMEM_STAT_COND_ADD(cond, stat)		/* nothing */
#endif	/* KMEM_STATS */

/*
 * kmem slab consolidator thresholds (tunables)
 */
static size_t kmem_frag_minslabs = 101;	/* minimum total slabs */
static size_t kmem_frag_numer = 1;	/* free buffers (numerator) */
static size_t kmem_frag_denom = KMEM_VOID_FRACTION; /* buffers (denominator) */
/*
 * Maximum number of slabs from which to move buffers during a single
 * maintenance interval while the system is not low on memory.
 */
static size_t kmem_reclaim_max_slabs = 1;
/*
 * Number of slabs to scan backwards from the end of the partial slab list
 * when searching for buffers to relocate.
 */
static size_t kmem_reclaim_scan_range = 12;

#ifdef	KMEM_STATS
static struct {
	uint64_t kms_callbacks;
	uint64_t kms_yes;
	uint64_t kms_no;
	uint64_t kms_later;
	uint64_t kms_dont_need;
	uint64_t kms_dont_know;
	uint64_t kms_hunt_found_slab;
	uint64_t kms_hunt_found_mag;
	uint64_t kms_hunt_alloc_fail;
	uint64_t kms_hunt_lucky;
	uint64_t kms_notify;
	uint64_t kms_notify_callbacks;
	uint64_t kms_disbelief;
	uint64_t kms_already_pending;
	uint64_t kms_callback_alloc_fail;
	uint64_t kms_callback_taskq_fail;
	uint64_t kms_endscan_slab_destroyed;
	uint64_t kms_endscan_nomem;
	uint64_t kms_endscan_slab_all_used;
	uint64_t kms_endscan_refcnt_changed;
	uint64_t kms_endscan_nomove_changed;
	uint64_t kms_endscan_freelist;
	uint64_t kms_avl_update;
	uint64_t kms_avl_noupdate;
	uint64_t kms_no_longer_reclaimable;
	uint64_t kms_notify_no_longer_reclaimable;
	uint64_t kms_alloc_fail;
	uint64_t kms_constructor_fail;
	uint64_t kms_dead_slabs_freed;
	uint64_t kms_defrags;
	uint64_t kms_scan_depot_ws_reaps;
	uint64_t kms_debug_reaps;
	uint64_t kms_debug_move_scans;
} kmem_move_stats;
#endif	/* KMEM_STATS */

/* consolidator knobs */
static boolean_t kmem_move_noreap;
static boolean_t kmem_move_blocked;
static boolean_t kmem_move_fulltilt;
static boolean_t kmem_move_any_partial;

#ifdef	DEBUG
/*
 * Ensure code coverage by occasionally running the consolidator even when the
 * caches are not fragmented (they may never be). These intervals are mean time
 * in cache maintenance intervals (kmem_cache_update).
 */
static int kmem_mtb_move = 60;		/* defrag 1 slab (~15min) */
static int kmem_mtb_reap = 1800;	/* defrag all slabs (~7.5hrs) */
#endif	/* DEBUG */

static kmem_cache_t	*kmem_defrag_cache;
static kmem_cache_t	*kmem_move_cache;
static taskq_t		*kmem_move_taskq;

static void kmem_cache_scan(kmem_cache_t *);
static void kmem_cache_defrag(kmem_cache_t *);


kmem_log_header_t	*kmem_transaction_log;
kmem_log_header_t	*kmem_content_log;
kmem_log_header_t	*kmem_failure_log;
kmem_log_header_t	*kmem_slab_log;

static int		kmem_lite_count; /* # of PCs in kmem_buftag_lite_t */

#define	KMEM_BUFTAG_LITE_ENTER(bt, count, caller)			\
	if ((count) > 0) {						\
		pc_t *_s = ((kmem_buftag_lite_t *)(bt))->bt_history;	\
		pc_t *_e;						\
		/* memmove() the old entries down one notch */		\
		for (_e = &_s[(count) - 1]; _e > _s; _e--)		\
			*_e = *(_e - 1);				\
		*_s = (uintptr_t)(caller);				\
	}

#define	KMERR_MODIFIED	0	/* buffer modified while on freelist */
#define	KMERR_REDZONE	1	/* redzone violation (write past end of buf) */
#define	KMERR_DUPFREE	2	/* freed a buffer twice */
#define	KMERR_BADADDR	3	/* freed a bad (unallocated) address */
#define	KMERR_BADBUFTAG	4	/* buftag corrupted */
#define	KMERR_BADBUFCTL	5	/* bufctl corrupted */
#define	KMERR_BADCACHE	6	/* freed a buffer to the wrong cache */
#define	KMERR_BADSIZE	7	/* alloc size != free size */
#define	KMERR_BADBASE	8	/* buffer base address wrong */

struct {
	hrtime_t	kmp_timestamp;	/* timestamp of panic */
	int		kmp_error;	/* type of kmem error */
	void		*kmp_buffer;	/* buffer that induced panic */
	void		*kmp_realbuf;	/* real start address for buffer */
	kmem_cache_t	*kmp_cache;	/* buffer's cache according to client */
	kmem_cache_t	*kmp_realcache;	/* actual cache containing buffer */
	kmem_slab_t	*kmp_slab;	/* slab accoring to kmem_findslab() */
	kmem_bufctl_t	*kmp_bufctl;	/* bufctl */
} kmem_panic_info;


static void
copy_pattern(uint64_t pattern, void *buf_arg, size_t size)
{
	uint64_t *bufend = (uint64_t *)((char *)buf_arg + size);
	uint64_t *buf = buf_arg;

	while (buf < bufend)
		*buf++ = pattern;
}

static void *
verify_pattern(uint64_t pattern, void *buf_arg, size_t size)
{
	uint64_t *bufend = (uint64_t *)((char *)buf_arg + size);
	uint64_t *buf;

	for (buf = buf_arg; buf < bufend; buf++)
		if (*buf != pattern)
			return (buf);
	return (NULL);
}

static void *
verify_and_copy_pattern(uint64_t old, uint64_t new, void *buf_arg, size_t size)
{
	uint64_t *bufend = (uint64_t *)((char *)buf_arg + size);
	uint64_t *buf;

	for (buf = buf_arg; buf < bufend; buf++) {
		if (*buf != old) {
			copy_pattern(old, buf_arg,
			    (char *)buf - (char *)buf_arg);
			return (buf);
		}
		*buf = new;
	}

	return (NULL);
}

static void
kmem_cache_applyall(void (*func)(kmem_cache_t *), taskq_t *tq, int tqflag)
{
	kmem_cache_t *cp;

	mutex_enter(&kmem_cache_lock);
	for (cp = list_head(&kmem_caches); cp != NULL;
	    cp = list_next(&kmem_caches, cp))
		if (tq != NULL)
			(void) taskq_dispatch(tq, (task_func_t *)func, cp,
			    tqflag);
		else
			func(cp);
	mutex_exit(&kmem_cache_lock);
}

static void
kmem_cache_applyall_id(void (*func)(kmem_cache_t *), taskq_t *tq, int tqflag)
{
	kmem_cache_t *cp;

	mutex_enter(&kmem_cache_lock);
	for (cp = list_head(&kmem_caches); cp != NULL;
	    cp = list_next(&kmem_caches, cp)) {
		if (!(cp->cache_cflags & KMC_IDENTIFIER))
			continue;
		if (tq != NULL)
			(void) taskq_dispatch(tq, (task_func_t *)func, cp,
			    tqflag);
		else
			func(cp);
	}
	mutex_exit(&kmem_cache_lock);
}

/*
 * Debugging support.  Given a buffer address, find its slab.
 */
static kmem_slab_t *
kmem_findslab(kmem_cache_t *cp, void *buf)
{
	kmem_slab_t *sp;

	mutex_enter(&cp->cache_lock);
	for (sp = list_head(&cp->cache_complete_slabs); sp != NULL;
	    sp = list_next(&cp->cache_complete_slabs, sp)) {
		if (KMEM_SLAB_MEMBER(sp, buf)) {
			mutex_exit(&cp->cache_lock);
			return (sp);
		}
	}
	for (sp = avl_first(&cp->cache_partial_slabs); sp != NULL;
	    sp = AVL_NEXT(&cp->cache_partial_slabs, sp)) {
		if (KMEM_SLAB_MEMBER(sp, buf)) {
			mutex_exit(&cp->cache_lock);
			return (sp);
		}
	}
	mutex_exit(&cp->cache_lock);

	return (NULL);
}

static void
kmem_error(int error, kmem_cache_t *cparg, void *bufarg)
{
	kmem_buftag_t *btp = NULL;
	kmem_bufctl_t *bcp = NULL;
	kmem_cache_t *cp = cparg;
	kmem_slab_t *sp;
	uint64_t *off;
	void *buf = bufarg;

	kmem_logging = 0;	/* stop logging when a bad thing happens */

	kmem_panic_info.kmp_timestamp = gethrtime();

	sp = kmem_findslab(cp, buf);
	if (sp == NULL) {
		for (cp = list_tail(&kmem_caches); cp != NULL;
		    cp = list_prev(&kmem_caches, cp)) {
			if ((sp = kmem_findslab(cp, buf)) != NULL)
				break;
		}
	}

	if (sp == NULL) {
		cp = NULL;
		error = KMERR_BADADDR;
	} else {
		if (cp != cparg)
			error = KMERR_BADCACHE;
		else
			buf = (char *)bufarg - ((uintptr_t)bufarg -
			    (uintptr_t)sp->slab_base) % cp->cache_chunksize;
		if (buf != bufarg)
			error = KMERR_BADBASE;
		if (cp->cache_flags & KMF_BUFTAG)
			btp = KMEM_BUFTAG(cp, buf);
		if (cp->cache_flags & KMF_HASH) {
			mutex_enter(&cp->cache_lock);
			for (bcp = *KMEM_HASH(cp, buf); bcp; bcp = bcp->bc_next)
				if (bcp->bc_addr == buf)
					break;
			mutex_exit(&cp->cache_lock);
			if (bcp == NULL && btp != NULL)
				bcp = btp->bt_bufctl;
			if (kmem_findslab(cp->cache_bufctl_cache, bcp) ==
			    NULL || P2PHASE((uintptr_t)bcp, KMEM_ALIGN) ||
			    bcp->bc_addr != buf) {
				error = KMERR_BADBUFCTL;
				bcp = NULL;
			}
		}
	}

	kmem_panic_info.kmp_error = error;
	kmem_panic_info.kmp_buffer = bufarg;
	kmem_panic_info.kmp_realbuf = buf;
	kmem_panic_info.kmp_cache = cparg;
	kmem_panic_info.kmp_realcache = cp;
	kmem_panic_info.kmp_slab = sp;
	kmem_panic_info.kmp_bufctl = bcp;

	printf("kernel memory allocator: ");

	switch (error) {

	case KMERR_MODIFIED:
		printf("buffer modified after being freed\n");
		off = verify_pattern(KMEM_FREE_PATTERN, buf, cp->cache_verify);
		if (off == NULL)	/* shouldn't happen */
			off = buf;
		printf("modification occurred at offset 0x%lx "
		    "(0x%llx replaced by 0x%llx)\n",
		    (uintptr_t)off - (uintptr_t)buf,
		    (longlong_t)KMEM_FREE_PATTERN, (longlong_t)*off);
		break;

	case KMERR_REDZONE:
		printf("redzone violation: write past end of buffer\n");
		break;

	case KMERR_BADADDR:
		printf("invalid free: buffer not in cache\n");
		break;

	case KMERR_DUPFREE:
		printf("duplicate free: buffer freed twice\n");
		break;

	case KMERR_BADBUFTAG:
		printf("boundary tag corrupted\n");
		printf("bcp ^ bxstat = %lx, should be %lx\n",
		    (intptr_t)btp->bt_bufctl ^ btp->bt_bxstat,
		    KMEM_BUFTAG_FREE);
		break;

	case KMERR_BADBUFCTL:
		printf("bufctl corrupted\n");
		break;

	case KMERR_BADCACHE:
		printf("buffer freed to wrong cache\n");
		printf("buffer was allocated from %s,\n", cp->cache_name);
		printf("caller attempting free to %s.\n", cparg->cache_name);
		break;

	case KMERR_BADSIZE:
		printf("bad free: free size (%u) != alloc size (%u)\n",
		    KMEM_SIZE_DECODE(((uint32_t *)btp)[0]),
		    KMEM_SIZE_DECODE(((uint32_t *)btp)[1]));
		break;

	case KMERR_BADBASE:
		printf("bad free: free address (%p) != alloc address (%p)\n",
		    bufarg, buf);
		break;
	}

	printf("buffer=%p  bufctl=%p  cache: %s\n",
	    bufarg, (void *)bcp, cparg->cache_name);

	if (bcp != NULL && (cp->cache_flags & KMF_AUDIT) &&
	    error != KMERR_BADBUFCTL) {
		int d;
		timestruc_t ts;
		kmem_bufctl_audit_t *bcap = (kmem_bufctl_audit_t *)bcp;

		hrt2ts(kmem_panic_info.kmp_timestamp - bcap->bc_timestamp, &ts);
		printf("previous transaction on buffer %p:\n", buf);
		printf("thread=%p  time=T-%ld.%09ld  slab=%p  cache: %s\n",
		    (void *)bcap->bc_thread, ts.tv_sec, ts.tv_nsec,
		    (void *)sp, cp->cache_name);
		for (d = 0; d < MIN(bcap->bc_depth, KMEM_STACK_DEPTH); d++) {
			ulong_t off;
			char *sym = kobj_getsymname(bcap->bc_stack[d], &off);
			printf("%s+%lx\n", sym ? sym : "?", off);
		}
	}
	if (kmem_panic > 0)
		panic("kernel heap corruption detected");
	if (kmem_panic == 0)
		debug_enter(NULL);
	kmem_logging = 1;	/* resume logging */
}

static kmem_log_header_t *
kmem_log_init(size_t logsize)
{
	kmem_log_header_t *lhp;
	int nchunks = 4 * max_ncpus;
	size_t lhsize = (size_t)&((kmem_log_header_t *)0)->lh_cpu[max_ncpus];
	int i;

	/*
	 * Make sure that lhp->lh_cpu[] is nicely aligned
	 * to prevent false sharing of cache lines.
	 */
	lhsize = P2ROUNDUP(lhsize, KMEM_ALIGN);
	lhp = vmem_xalloc(kmem_log_arena, lhsize, 64, P2NPHASE(lhsize, 64), 0,
	    NULL, NULL, VM_SLEEP);
	bzero(lhp, lhsize);

	mutex_init(&lhp->lh_lock, NULL, MUTEX_DEFAULT, NULL);
	lhp->lh_nchunks = nchunks;
	lhp->lh_chunksize = P2ROUNDUP(logsize / nchunks + 1, PAGESIZE);
	lhp->lh_base = vmem_alloc(kmem_log_arena,
	    lhp->lh_chunksize * nchunks, VM_SLEEP);
	lhp->lh_free = vmem_alloc(kmem_log_arena,
	    nchunks * sizeof (int), VM_SLEEP);
	bzero(lhp->lh_base, lhp->lh_chunksize * nchunks);

	for (i = 0; i < max_ncpus; i++) {
		kmem_cpu_log_header_t *clhp = &lhp->lh_cpu[i];
		mutex_init(&clhp->clh_lock, NULL, MUTEX_DEFAULT, NULL);
		clhp->clh_chunk = i;
	}

	for (i = max_ncpus; i < nchunks; i++)
		lhp->lh_free[i] = i;

	lhp->lh_head = max_ncpus;
	lhp->lh_tail = 0;

	return (lhp);
}

static void *
kmem_log_enter(kmem_log_header_t *lhp, void *data, size_t size)
{
	void *logspace;
	kmem_cpu_log_header_t *clhp = &lhp->lh_cpu[CPU->cpu_seqid];

	if (lhp == NULL || kmem_logging == 0 || panicstr)
		return (NULL);

	mutex_enter(&clhp->clh_lock);
	clhp->clh_hits++;
	if (size > clhp->clh_avail) {
		mutex_enter(&lhp->lh_lock);
		lhp->lh_hits++;
		lhp->lh_free[lhp->lh_tail] = clhp->clh_chunk;
		lhp->lh_tail = (lhp->lh_tail + 1) % lhp->lh_nchunks;
		clhp->clh_chunk = lhp->lh_free[lhp->lh_head];
		lhp->lh_head = (lhp->lh_head + 1) % lhp->lh_nchunks;
		clhp->clh_current = lhp->lh_base +
		    clhp->clh_chunk * lhp->lh_chunksize;
		clhp->clh_avail = lhp->lh_chunksize;
		if (size > lhp->lh_chunksize)
			size = lhp->lh_chunksize;
		mutex_exit(&lhp->lh_lock);
	}
	logspace = clhp->clh_current;
	clhp->clh_current += size;
	clhp->clh_avail -= size;
	bcopy(data, logspace, size);
	mutex_exit(&clhp->clh_lock);
	return (logspace);
}

#define	KMEM_AUDIT(lp, cp, bcp)						\
{									\
	kmem_bufctl_audit_t *_bcp = (kmem_bufctl_audit_t *)(bcp);	\
	_bcp->bc_timestamp = gethrtime();				\
	_bcp->bc_thread = curthread;					\
	_bcp->bc_depth = getpcstack(_bcp->bc_stack, KMEM_STACK_DEPTH);	\
	_bcp->bc_lastlog = kmem_log_enter((lp), _bcp, sizeof (*_bcp));	\
}

static void
kmem_log_event(kmem_log_header_t *lp, kmem_cache_t *cp,
	kmem_slab_t *sp, void *addr)
{
	kmem_bufctl_audit_t bca;

	bzero(&bca, sizeof (kmem_bufctl_audit_t));
	bca.bc_addr = addr;
	bca.bc_slab = sp;
	bca.bc_cache = cp;
	KMEM_AUDIT(lp, cp, &bca);
}

/*
 * Create a new slab for cache cp.
 */
static kmem_slab_t *
kmem_slab_create(kmem_cache_t *cp, int kmflag)
{
	size_t slabsize = cp->cache_slabsize;
	size_t chunksize = cp->cache_chunksize;
	int cache_flags = cp->cache_flags;
	size_t color, chunks;
	char *buf, *slab;
	kmem_slab_t *sp;
	kmem_bufctl_t *bcp;
	vmem_t *vmp = cp->cache_arena;

	ASSERT(MUTEX_NOT_HELD(&cp->cache_lock));

	color = cp->cache_color + cp->cache_align;
	if (color > cp->cache_maxcolor)
		color = cp->cache_mincolor;
	cp->cache_color = color;

	slab = vmem_alloc(vmp, slabsize, kmflag & KM_VMFLAGS);

	if (slab == NULL)
		goto vmem_alloc_failure;

	ASSERT(P2PHASE((uintptr_t)slab, vmp->vm_quantum) == 0);

	/*
	 * Reverify what was already checked in kmem_cache_set_move(), since the
	 * consolidator depends (for correctness) on slabs being initialized
	 * with the 0xbaddcafe memory pattern (setting a low order bit usable by
	 * clients to distinguish uninitialized memory from known objects).
	 */
	ASSERT((cp->cache_move == NULL) || !(cp->cache_cflags & KMC_NOTOUCH));
	if (!(cp->cache_cflags & KMC_NOTOUCH))
		copy_pattern(KMEM_UNINITIALIZED_PATTERN, slab, slabsize);

	if (cache_flags & KMF_HASH) {
		if ((sp = kmem_cache_alloc(kmem_slab_cache, kmflag)) == NULL)
			goto slab_alloc_failure;
		chunks = (slabsize - color) / chunksize;
	} else {
		sp = KMEM_SLAB(cp, slab);
		chunks = (slabsize - sizeof (kmem_slab_t) - color) / chunksize;
	}

	sp->slab_cache	= cp;
	sp->slab_head	= NULL;
	sp->slab_refcnt	= 0;
	sp->slab_base	= buf = slab + color;
	sp->slab_chunks	= chunks;
	sp->slab_stuck_offset = (uint32_t)-1;
	sp->slab_later_count = 0;
	sp->slab_flags = 0;

	ASSERT(chunks > 0);
	while (chunks-- != 0) {
		if (cache_flags & KMF_HASH) {
			bcp = kmem_cache_alloc(cp->cache_bufctl_cache, kmflag);
			if (bcp == NULL)
				goto bufctl_alloc_failure;
			if (cache_flags & KMF_AUDIT) {
				kmem_bufctl_audit_t *bcap =
				    (kmem_bufctl_audit_t *)bcp;
				bzero(bcap, sizeof (kmem_bufctl_audit_t));
				bcap->bc_cache = cp;
			}
			bcp->bc_addr = buf;
			bcp->bc_slab = sp;
		} else {
			bcp = KMEM_BUFCTL(cp, buf);
		}
		if (cache_flags & KMF_BUFTAG) {
			kmem_buftag_t *btp = KMEM_BUFTAG(cp, buf);
			btp->bt_redzone = KMEM_REDZONE_PATTERN;
			btp->bt_bufctl = bcp;
			btp->bt_bxstat = (intptr_t)bcp ^ KMEM_BUFTAG_FREE;
			if (cache_flags & KMF_DEADBEEF) {
				copy_pattern(KMEM_FREE_PATTERN, buf,
				    cp->cache_verify);
			}
		}
		bcp->bc_next = sp->slab_head;
		sp->slab_head = bcp;
		buf += chunksize;
	}

	kmem_log_event(kmem_slab_log, cp, sp, slab);

	return (sp);

bufctl_alloc_failure:

	while ((bcp = sp->slab_head) != NULL) {
		sp->slab_head = bcp->bc_next;
		kmem_cache_free(cp->cache_bufctl_cache, bcp);
	}
	kmem_cache_free(kmem_slab_cache, sp);

slab_alloc_failure:

	vmem_free(vmp, slab, slabsize);

vmem_alloc_failure:

	kmem_log_event(kmem_failure_log, cp, NULL, NULL);
	atomic_add_64(&cp->cache_alloc_fail, 1);

	return (NULL);
}

/*
 * Destroy a slab.
 */
static void
kmem_slab_destroy(kmem_cache_t *cp, kmem_slab_t *sp)
{
	vmem_t *vmp = cp->cache_arena;
	void *slab = (void *)P2ALIGN((uintptr_t)sp->slab_base, vmp->vm_quantum);

	ASSERT(MUTEX_NOT_HELD(&cp->cache_lock));
	ASSERT(sp->slab_refcnt == 0);

	if (cp->cache_flags & KMF_HASH) {
		kmem_bufctl_t *bcp;
		while ((bcp = sp->slab_head) != NULL) {
			sp->slab_head = bcp->bc_next;
			kmem_cache_free(cp->cache_bufctl_cache, bcp);
		}
		kmem_cache_free(kmem_slab_cache, sp);
	}
	vmem_free(vmp, slab, cp->cache_slabsize);
}

static void *
kmem_slab_alloc_impl(kmem_cache_t *cp, kmem_slab_t *sp)
{
	kmem_bufctl_t *bcp, **hash_bucket;
	void *buf;

	ASSERT(MUTEX_HELD(&cp->cache_lock));
	/*
	 * kmem_slab_alloc() drops cache_lock when it creates a new slab, so we
	 * can't ASSERT(avl_is_empty(&cp->cache_partial_slabs)) here when the
	 * slab is newly created (sp->slab_refcnt == 0).
	 */
	ASSERT((sp->slab_refcnt == 0) || (KMEM_SLAB_IS_PARTIAL(sp) &&
	    (sp == avl_first(&cp->cache_partial_slabs))));
	ASSERT(sp->slab_cache == cp);

	cp->cache_slab_alloc++;
	cp->cache_bufslab--;
	sp->slab_refcnt++;

	bcp = sp->slab_head;
	if ((sp->slab_head = bcp->bc_next) == NULL) {
		ASSERT(KMEM_SLAB_IS_ALL_USED(sp));
		if (sp->slab_refcnt == 1) {
			ASSERT(sp->slab_chunks == 1);
		} else {
			ASSERT(sp->slab_chunks > 1); /* the slab was partial */
			avl_remove(&cp->cache_partial_slabs, sp);
			sp->slab_later_count = 0; /* clear history */
			sp->slab_flags &= ~KMEM_SLAB_NOMOVE;
			sp->slab_stuck_offset = (uint32_t)-1;
		}
		list_insert_head(&cp->cache_complete_slabs, sp);
		cp->cache_complete_slab_count++;
	} else {
		ASSERT(KMEM_SLAB_IS_PARTIAL(sp));
		if (sp->slab_refcnt == 1) {
			avl_add(&cp->cache_partial_slabs, sp);
		} else {
			/*
			 * The slab is now more allocated than it was, so the
			 * order remains unchanged.
			 */
			ASSERT(!avl_update(&cp->cache_partial_slabs, sp));
		}
	}

	if (cp->cache_flags & KMF_HASH) {
		/*
		 * Add buffer to allocated-address hash table.
		 */
		buf = bcp->bc_addr;
		hash_bucket = KMEM_HASH(cp, buf);
		bcp->bc_next = *hash_bucket;
		*hash_bucket = bcp;
		if ((cp->cache_flags & (KMF_AUDIT | KMF_BUFTAG)) == KMF_AUDIT) {
			KMEM_AUDIT(kmem_transaction_log, cp, bcp);
		}
	} else {
		buf = KMEM_BUF(cp, bcp);
	}

	ASSERT(KMEM_SLAB_MEMBER(sp, buf));
	return (buf);
}

/*
 * Allocate a raw (unconstructed) buffer from cp's slab layer.
 */
static void *
kmem_slab_alloc(kmem_cache_t *cp, int kmflag)
{
	kmem_slab_t *sp;
	void *buf;
	boolean_t test_destructor;

	mutex_enter(&cp->cache_lock);
	test_destructor = (cp->cache_slab_alloc == 0);
	sp = avl_first(&cp->cache_partial_slabs);
	if (sp == NULL) {
		ASSERT(cp->cache_bufslab == 0);

		/*
		 * The freelist is empty.  Create a new slab.
		 */
		mutex_exit(&cp->cache_lock);
		if ((sp = kmem_slab_create(cp, kmflag)) == NULL) {
			return (NULL);
		}
		mutex_enter(&cp->cache_lock);
		cp->cache_slab_create++;
		if ((cp->cache_buftotal += sp->slab_chunks) > cp->cache_bufmax)
			cp->cache_bufmax = cp->cache_buftotal;
		cp->cache_bufslab += sp->slab_chunks;
	}

	buf = kmem_slab_alloc_impl(cp, sp);
	ASSERT((cp->cache_slab_create - cp->cache_slab_destroy) ==
	    (cp->cache_complete_slab_count +
	    avl_numnodes(&cp->cache_partial_slabs) +
	    (cp->cache_defrag == NULL ? 0 : cp->cache_defrag->kmd_deadcount)));
	mutex_exit(&cp->cache_lock);

	if (test_destructor && cp->cache_destructor != NULL) {
		/*
		 * On the first kmem_slab_alloc(), assert that it is valid to
		 * call the destructor on a newly constructed object without any
		 * client involvement.
		 */
		if ((cp->cache_constructor == NULL) ||
		    cp->cache_constructor(buf, cp->cache_private,
		    kmflag) == 0) {
			cp->cache_destructor(buf, cp->cache_private);
		}
		copy_pattern(KMEM_UNINITIALIZED_PATTERN, buf,
		    cp->cache_bufsize);
		if (cp->cache_flags & KMF_DEADBEEF) {
			copy_pattern(KMEM_FREE_PATTERN, buf, cp->cache_verify);
		}
	}

	return (buf);
}

static void kmem_slab_move_yes(kmem_cache_t *, kmem_slab_t *, void *);

/*
 * Free a raw (unconstructed) buffer to cp's slab layer.
 */
static void
kmem_slab_free(kmem_cache_t *cp, void *buf)
{
	kmem_slab_t *sp;
	kmem_bufctl_t *bcp, **prev_bcpp;

	ASSERT(buf != NULL);

	mutex_enter(&cp->cache_lock);
	cp->cache_slab_free++;

	if (cp->cache_flags & KMF_HASH) {
		/*
		 * Look up buffer in allocated-address hash table.
		 */
		prev_bcpp = KMEM_HASH(cp, buf);
		while ((bcp = *prev_bcpp) != NULL) {
			if (bcp->bc_addr == buf) {
				*prev_bcpp = bcp->bc_next;
				sp = bcp->bc_slab;
				break;
			}
			cp->cache_lookup_depth++;
			prev_bcpp = &bcp->bc_next;
		}
	} else {
		bcp = KMEM_BUFCTL(cp, buf);
		sp = KMEM_SLAB(cp, buf);
	}

	if (bcp == NULL || sp->slab_cache != cp || !KMEM_SLAB_MEMBER(sp, buf)) {
		mutex_exit(&cp->cache_lock);
		kmem_error(KMERR_BADADDR, cp, buf);
		return;
	}

	if (KMEM_SLAB_OFFSET(sp, buf) == sp->slab_stuck_offset) {
		/*
		 * If this is the buffer that prevented the consolidator from
		 * clearing the slab, we can reset the slab flags now that the
		 * buffer is freed. (It makes sense to do this in
		 * kmem_cache_free(), where the client gives up ownership of the
		 * buffer, but on the hot path the test is too expensive.)
		 */
		kmem_slab_move_yes(cp, sp, buf);
	}

	if ((cp->cache_flags & (KMF_AUDIT | KMF_BUFTAG)) == KMF_AUDIT) {
		if (cp->cache_flags & KMF_CONTENTS)
			((kmem_bufctl_audit_t *)bcp)->bc_contents =
			    kmem_log_enter(kmem_content_log, buf,
			    cp->cache_contents);
		KMEM_AUDIT(kmem_transaction_log, cp, bcp);
	}

	bcp->bc_next = sp->slab_head;
	sp->slab_head = bcp;

	cp->cache_bufslab++;
	ASSERT(sp->slab_refcnt >= 1);

	if (--sp->slab_refcnt == 0) {
		/*
		 * There are no outstanding allocations from this slab,
		 * so we can reclaim the memory.
		 */
		if (sp->slab_chunks == 1) {
			list_remove(&cp->cache_complete_slabs, sp);
			cp->cache_complete_slab_count--;
		} else {
			avl_remove(&cp->cache_partial_slabs, sp);
		}

		cp->cache_buftotal -= sp->slab_chunks;
		cp->cache_bufslab -= sp->slab_chunks;
		/*
		 * Defer releasing the slab to the virtual memory subsystem
		 * while there is a pending move callback, since we guarantee
		 * that buffers passed to the move callback have only been
		 * touched by kmem or by the client itself. Since the memory
		 * patterns baddcafe (uninitialized) and deadbeef (freed) both
		 * set at least one of the two lowest order bits, the client can
		 * test those bits in the move callback to determine whether or
		 * not it knows about the buffer (assuming that the client also
		 * sets one of those low order bits whenever it frees a buffer).
		 */
		if (cp->cache_defrag == NULL ||
		    (avl_is_empty(&cp->cache_defrag->kmd_moves_pending) &&
		    !(sp->slab_flags & KMEM_SLAB_MOVE_PENDING))) {
			cp->cache_slab_destroy++;
			mutex_exit(&cp->cache_lock);
			kmem_slab_destroy(cp, sp);
		} else {
			list_t *deadlist = &cp->cache_defrag->kmd_deadlist;
			/*
			 * Slabs are inserted at both ends of the deadlist to
			 * distinguish between slabs freed while move callbacks
			 * are pending (list head) and a slab freed while the
			 * lock is dropped in kmem_move_buffers() (list tail) so
			 * that in both cases slab_destroy() is called from the
			 * right context.
			 */
			if (sp->slab_flags & KMEM_SLAB_MOVE_PENDING) {
				list_insert_tail(deadlist, sp);
			} else {
				list_insert_head(deadlist, sp);
			}
			cp->cache_defrag->kmd_deadcount++;
			mutex_exit(&cp->cache_lock);
		}
		return;
	}

	if (bcp->bc_next == NULL) {
		/* Transition the slab from completely allocated to partial. */
		ASSERT(sp->slab_refcnt == (sp->slab_chunks - 1));
		ASSERT(sp->slab_chunks > 1);
		list_remove(&cp->cache_complete_slabs, sp);
		cp->cache_complete_slab_count--;
		avl_add(&cp->cache_partial_slabs, sp);
	} else {
#ifdef	DEBUG
		if (avl_update_gt(&cp->cache_partial_slabs, sp)) {
			KMEM_STAT_ADD(kmem_move_stats.kms_avl_update);
		} else {
			KMEM_STAT_ADD(kmem_move_stats.kms_avl_noupdate);
		}
#else
		(void) avl_update_gt(&cp->cache_partial_slabs, sp);
#endif
	}

	ASSERT((cp->cache_slab_create - cp->cache_slab_destroy) ==
	    (cp->cache_complete_slab_count +
	    avl_numnodes(&cp->cache_partial_slabs) +
	    (cp->cache_defrag == NULL ? 0 : cp->cache_defrag->kmd_deadcount)));
	mutex_exit(&cp->cache_lock);
}

/*
 * Return -1 if kmem_error, 1 if constructor fails, 0 if successful.
 */
static int
kmem_cache_alloc_debug(kmem_cache_t *cp, void *buf, int kmflag, int construct,
    caddr_t caller)
{
	kmem_buftag_t *btp = KMEM_BUFTAG(cp, buf);
	kmem_bufctl_audit_t *bcp = (kmem_bufctl_audit_t *)btp->bt_bufctl;
	uint32_t mtbf;

	if (btp->bt_bxstat != ((intptr_t)bcp ^ KMEM_BUFTAG_FREE)) {
		kmem_error(KMERR_BADBUFTAG, cp, buf);
		return (-1);
	}

	btp->bt_bxstat = (intptr_t)bcp ^ KMEM_BUFTAG_ALLOC;

	if ((cp->cache_flags & KMF_HASH) && bcp->bc_addr != buf) {
		kmem_error(KMERR_BADBUFCTL, cp, buf);
		return (-1);
	}

	if (cp->cache_flags & KMF_DEADBEEF) {
		if (!construct && (cp->cache_flags & KMF_LITE)) {
			if (*(uint64_t *)buf != KMEM_FREE_PATTERN) {
				kmem_error(KMERR_MODIFIED, cp, buf);
				return (-1);
			}
			if (cp->cache_constructor != NULL)
				*(uint64_t *)buf = btp->bt_redzone;
			else
				*(uint64_t *)buf = KMEM_UNINITIALIZED_PATTERN;
		} else {
			construct = 1;
			if (verify_and_copy_pattern(KMEM_FREE_PATTERN,
			    KMEM_UNINITIALIZED_PATTERN, buf,
			    cp->cache_verify)) {
				kmem_error(KMERR_MODIFIED, cp, buf);
				return (-1);
			}
		}
	}
	btp->bt_redzone = KMEM_REDZONE_PATTERN;

	if ((mtbf = kmem_mtbf | cp->cache_mtbf) != 0 &&
	    gethrtime() % mtbf == 0 &&
	    (kmflag & (KM_NOSLEEP | KM_PANIC)) == KM_NOSLEEP) {
		kmem_log_event(kmem_failure_log, cp, NULL, NULL);
		if (!construct && cp->cache_destructor != NULL)
			cp->cache_destructor(buf, cp->cache_private);
	} else {
		mtbf = 0;
	}

	if (mtbf || (construct && cp->cache_constructor != NULL &&
	    cp->cache_constructor(buf, cp->cache_private, kmflag) != 0)) {
		atomic_add_64(&cp->cache_alloc_fail, 1);
		btp->bt_bxstat = (intptr_t)bcp ^ KMEM_BUFTAG_FREE;
		if (cp->cache_flags & KMF_DEADBEEF)
			copy_pattern(KMEM_FREE_PATTERN, buf, cp->cache_verify);
		kmem_slab_free(cp, buf);
		return (1);
	}

	if (cp->cache_flags & KMF_AUDIT) {
		KMEM_AUDIT(kmem_transaction_log, cp, bcp);
	}

	if ((cp->cache_flags & KMF_LITE) &&
	    !(cp->cache_cflags & KMC_KMEM_ALLOC)) {
		KMEM_BUFTAG_LITE_ENTER(btp, kmem_lite_count, caller);
	}

	return (0);
}

static int
kmem_cache_free_debug(kmem_cache_t *cp, void *buf, caddr_t caller)
{
	kmem_buftag_t *btp = KMEM_BUFTAG(cp, buf);
	kmem_bufctl_audit_t *bcp = (kmem_bufctl_audit_t *)btp->bt_bufctl;
	kmem_slab_t *sp;

	if (btp->bt_bxstat != ((intptr_t)bcp ^ KMEM_BUFTAG_ALLOC)) {
		if (btp->bt_bxstat == ((intptr_t)bcp ^ KMEM_BUFTAG_FREE)) {
			kmem_error(KMERR_DUPFREE, cp, buf);
			return (-1);
		}
		sp = kmem_findslab(cp, buf);
		if (sp == NULL || sp->slab_cache != cp)
			kmem_error(KMERR_BADADDR, cp, buf);
		else
			kmem_error(KMERR_REDZONE, cp, buf);
		return (-1);
	}

	btp->bt_bxstat = (intptr_t)bcp ^ KMEM_BUFTAG_FREE;

	if ((cp->cache_flags & KMF_HASH) && bcp->bc_addr != buf) {
		kmem_error(KMERR_BADBUFCTL, cp, buf);
		return (-1);
	}

	if (btp->bt_redzone != KMEM_REDZONE_PATTERN) {
		kmem_error(KMERR_REDZONE, cp, buf);
		return (-1);
	}

	if (cp->cache_flags & KMF_AUDIT) {
		if (cp->cache_flags & KMF_CONTENTS)
			bcp->bc_contents = kmem_log_enter(kmem_content_log,
			    buf, cp->cache_contents);
		KMEM_AUDIT(kmem_transaction_log, cp, bcp);
	}

	if ((cp->cache_flags & KMF_LITE) &&
	    !(cp->cache_cflags & KMC_KMEM_ALLOC)) {
		KMEM_BUFTAG_LITE_ENTER(btp, kmem_lite_count, caller);
	}

	if (cp->cache_flags & KMF_DEADBEEF) {
		if (cp->cache_flags & KMF_LITE)
			btp->bt_redzone = *(uint64_t *)buf;
		else if (cp->cache_destructor != NULL)
			cp->cache_destructor(buf, cp->cache_private);

		copy_pattern(KMEM_FREE_PATTERN, buf, cp->cache_verify);
	}

	return (0);
}

/*
 * Free each object in magazine mp to cp's slab layer, and free mp itself.
 */
static void
kmem_magazine_destroy(kmem_cache_t *cp, kmem_magazine_t *mp, int nrounds)
{
	int round;

	ASSERT(!list_link_active(&cp->cache_link) ||
	    taskq_member(kmem_taskq, curthread));

	for (round = 0; round < nrounds; round++) {
		void *buf = mp->mag_round[round];

		if (cp->cache_flags & KMF_DEADBEEF) {
			if (verify_pattern(KMEM_FREE_PATTERN, buf,
			    cp->cache_verify) != NULL) {
				kmem_error(KMERR_MODIFIED, cp, buf);
				continue;
			}
			if ((cp->cache_flags & KMF_LITE) &&
			    cp->cache_destructor != NULL) {
				kmem_buftag_t *btp = KMEM_BUFTAG(cp, buf);
				*(uint64_t *)buf = btp->bt_redzone;
				cp->cache_destructor(buf, cp->cache_private);
				*(uint64_t *)buf = KMEM_FREE_PATTERN;
			}
		} else if (cp->cache_destructor != NULL) {
			cp->cache_destructor(buf, cp->cache_private);
		}

		kmem_slab_free(cp, buf);
	}
	ASSERT(KMEM_MAGAZINE_VALID(cp, mp));
	kmem_cache_free(cp->cache_magtype->mt_cache, mp);
}

/*
 * Allocate a magazine from the depot.
 */
static kmem_magazine_t *
kmem_depot_alloc(kmem_cache_t *cp, kmem_maglist_t *mlp)
{
	kmem_magazine_t *mp;

	/*
	 * If we can't get the depot lock without contention,
	 * update our contention count.  We use the depot
	 * contention rate to determine whether we need to
	 * increase the magazine size for better scalability.
	 */
	if (!mutex_tryenter(&cp->cache_depot_lock)) {
		mutex_enter(&cp->cache_depot_lock);
		cp->cache_depot_contention++;
	}

	if ((mp = mlp->ml_list) != NULL) {
		ASSERT(KMEM_MAGAZINE_VALID(cp, mp));
		mlp->ml_list = mp->mag_next;
		if (--mlp->ml_total < mlp->ml_min)
			mlp->ml_min = mlp->ml_total;
		mlp->ml_alloc++;
	}

	mutex_exit(&cp->cache_depot_lock);

	return (mp);
}

/*
 * Free a magazine to the depot.
 */
static void
kmem_depot_free(kmem_cache_t *cp, kmem_maglist_t *mlp, kmem_magazine_t *mp)
{
	mutex_enter(&cp->cache_depot_lock);
	ASSERT(KMEM_MAGAZINE_VALID(cp, mp));
	mp->mag_next = mlp->ml_list;
	mlp->ml_list = mp;
	mlp->ml_total++;
	mutex_exit(&cp->cache_depot_lock);
}

/*
 * Update the working set statistics for cp's depot.
 */
static void
kmem_depot_ws_update(kmem_cache_t *cp)
{
	mutex_enter(&cp->cache_depot_lock);
	cp->cache_full.ml_reaplimit = cp->cache_full.ml_min;
	cp->cache_full.ml_min = cp->cache_full.ml_total;
	cp->cache_empty.ml_reaplimit = cp->cache_empty.ml_min;
	cp->cache_empty.ml_min = cp->cache_empty.ml_total;
	mutex_exit(&cp->cache_depot_lock);
}

/*
 * Reap all magazines that have fallen out of the depot's working set.
 */
static void
kmem_depot_ws_reap(kmem_cache_t *cp)
{
	long reap;
	kmem_magazine_t *mp;

	ASSERT(!list_link_active(&cp->cache_link) ||
	    taskq_member(kmem_taskq, curthread));

	reap = MIN(cp->cache_full.ml_reaplimit, cp->cache_full.ml_min);
	while (reap-- && (mp = kmem_depot_alloc(cp, &cp->cache_full)) != NULL)
		kmem_magazine_destroy(cp, mp, cp->cache_magtype->mt_magsize);

	reap = MIN(cp->cache_empty.ml_reaplimit, cp->cache_empty.ml_min);
	while (reap-- && (mp = kmem_depot_alloc(cp, &cp->cache_empty)) != NULL)
		kmem_magazine_destroy(cp, mp, 0);
}

static void
kmem_cpu_reload(kmem_cpu_cache_t *ccp, kmem_magazine_t *mp, int rounds)
{
	ASSERT((ccp->cc_loaded == NULL && ccp->cc_rounds == -1) ||
	    (ccp->cc_loaded && ccp->cc_rounds + rounds == ccp->cc_magsize));
	ASSERT(ccp->cc_magsize > 0);

	ccp->cc_ploaded = ccp->cc_loaded;
	ccp->cc_prounds = ccp->cc_rounds;
	ccp->cc_loaded = mp;
	ccp->cc_rounds = rounds;
}

/*
 * Allocate a constructed object from cache cp.
 */
void *
kmem_cache_alloc(kmem_cache_t *cp, int kmflag)
{
	kmem_cpu_cache_t *ccp = KMEM_CPU_CACHE(cp);
	kmem_magazine_t *fmp;
	void *buf;

	mutex_enter(&ccp->cc_lock);
	for (;;) {
		/*
		 * If there's an object available in the current CPU's
		 * loaded magazine, just take it and return.
		 */
		if (ccp->cc_rounds > 0) {
			buf = ccp->cc_loaded->mag_round[--ccp->cc_rounds];
			ccp->cc_alloc++;
			mutex_exit(&ccp->cc_lock);
			if ((ccp->cc_flags & KMF_BUFTAG) &&
			    kmem_cache_alloc_debug(cp, buf, kmflag, 0,
			    caller()) != 0) {
				if (kmflag & KM_NOSLEEP)
					return (NULL);
				mutex_enter(&ccp->cc_lock);
				continue;
			}
			return (buf);
		}

		/*
		 * The loaded magazine is empty.  If the previously loaded
		 * magazine was full, exchange them and try again.
		 */
		if (ccp->cc_prounds > 0) {
			kmem_cpu_reload(ccp, ccp->cc_ploaded, ccp->cc_prounds);
			continue;
		}

		/*
		 * If the magazine layer is disabled, break out now.
		 */
		if (ccp->cc_magsize == 0)
			break;

		/*
		 * Try to get a full magazine from the depot.
		 */
		fmp = kmem_depot_alloc(cp, &cp->cache_full);
		if (fmp != NULL) {
			if (ccp->cc_ploaded != NULL)
				kmem_depot_free(cp, &cp->cache_empty,
				    ccp->cc_ploaded);
			kmem_cpu_reload(ccp, fmp, ccp->cc_magsize);
			continue;
		}

		/*
		 * There are no full magazines in the depot,
		 * so fall through to the slab layer.
		 */
		break;
	}
	mutex_exit(&ccp->cc_lock);

	/*
	 * We couldn't allocate a constructed object from the magazine layer,
	 * so get a raw buffer from the slab layer and apply its constructor.
	 */
	buf = kmem_slab_alloc(cp, kmflag);

	if (buf == NULL)
		return (NULL);

	if (cp->cache_flags & KMF_BUFTAG) {
		/*
		 * Make kmem_cache_alloc_debug() apply the constructor for us.
		 */
		int rc = kmem_cache_alloc_debug(cp, buf, kmflag, 1, caller());
		if (rc != 0) {
			if (kmflag & KM_NOSLEEP)
				return (NULL);
			/*
			 * kmem_cache_alloc_debug() detected corruption
			 * but didn't panic (kmem_panic <= 0). We should not be
			 * here because the constructor failed (indicated by a
			 * return code of 1). Try again.
			 */
			ASSERT(rc == -1);
			return (kmem_cache_alloc(cp, kmflag));
		}
		return (buf);
	}

	if (cp->cache_constructor != NULL &&
	    cp->cache_constructor(buf, cp->cache_private, kmflag) != 0) {
		atomic_add_64(&cp->cache_alloc_fail, 1);
		kmem_slab_free(cp, buf);
		return (NULL);
	}

	return (buf);
}

/*
 * The freed argument tells whether or not kmem_cache_free_debug() has already
 * been called so that we can avoid the duplicate free error. For example, a
 * buffer on a magazine has already been freed by the client but is still
 * constructed.
 */
static void
kmem_slab_free_constructed(kmem_cache_t *cp, void *buf, boolean_t freed)
{
	if (!freed && (cp->cache_flags & KMF_BUFTAG))
		if (kmem_cache_free_debug(cp, buf, caller()) == -1)
			return;

	/*
	 * Note that if KMF_DEADBEEF is in effect and KMF_LITE is not,
	 * kmem_cache_free_debug() will have already applied the destructor.
	 */
	if ((cp->cache_flags & (KMF_DEADBEEF | KMF_LITE)) != KMF_DEADBEEF &&
	    cp->cache_destructor != NULL) {
		if (cp->cache_flags & KMF_DEADBEEF) {	/* KMF_LITE implied */
			kmem_buftag_t *btp = KMEM_BUFTAG(cp, buf);
			*(uint64_t *)buf = btp->bt_redzone;
			cp->cache_destructor(buf, cp->cache_private);
			*(uint64_t *)buf = KMEM_FREE_PATTERN;
		} else {
			cp->cache_destructor(buf, cp->cache_private);
		}
	}

	kmem_slab_free(cp, buf);
}

/*
 * Free a constructed object to cache cp.
 */
void
kmem_cache_free(kmem_cache_t *cp, void *buf)
{
	kmem_cpu_cache_t *ccp = KMEM_CPU_CACHE(cp);
	kmem_magazine_t *emp;
	kmem_magtype_t *mtp;

	/*
	 * The client must not free either of the buffers passed to the move
	 * callback function.
	 */
	ASSERT(cp->cache_defrag == NULL ||
	    cp->cache_defrag->kmd_thread != curthread ||
	    (buf != cp->cache_defrag->kmd_from_buf &&
	    buf != cp->cache_defrag->kmd_to_buf));

	if (ccp->cc_flags & KMF_BUFTAG)
		if (kmem_cache_free_debug(cp, buf, caller()) == -1)
			return;

	mutex_enter(&ccp->cc_lock);
	for (;;) {
		/*
		 * If there's a slot available in the current CPU's
		 * loaded magazine, just put the object there and return.
		 */
		if ((uint_t)ccp->cc_rounds < ccp->cc_magsize) {
			ccp->cc_loaded->mag_round[ccp->cc_rounds++] = buf;
			ccp->cc_free++;
			mutex_exit(&ccp->cc_lock);
			return;
		}

		/*
		 * The loaded magazine is full.  If the previously loaded
		 * magazine was empty, exchange them and try again.
		 */
		if (ccp->cc_prounds == 0) {
			kmem_cpu_reload(ccp, ccp->cc_ploaded, ccp->cc_prounds);
			continue;
		}

		/*
		 * If the magazine layer is disabled, break out now.
		 */
		if (ccp->cc_magsize == 0)
			break;

		/*
		 * Try to get an empty magazine from the depot.
		 */
		emp = kmem_depot_alloc(cp, &cp->cache_empty);
		if (emp != NULL) {
			if (ccp->cc_ploaded != NULL)
				kmem_depot_free(cp, &cp->cache_full,
				    ccp->cc_ploaded);
			kmem_cpu_reload(ccp, emp, 0);
			continue;
		}

		/*
		 * There are no empty magazines in the depot,
		 * so try to allocate a new one.  We must drop all locks
		 * across kmem_cache_alloc() because lower layers may
		 * attempt to allocate from this cache.
		 */
		mtp = cp->cache_magtype;
		mutex_exit(&ccp->cc_lock);
		emp = kmem_cache_alloc(mtp->mt_cache, KM_NOSLEEP);
		mutex_enter(&ccp->cc_lock);

		if (emp != NULL) {
			/*
			 * We successfully allocated an empty magazine.
			 * However, we had to drop ccp->cc_lock to do it,
			 * so the cache's magazine size may have changed.
			 * If so, free the magazine and try again.
			 */
			if (ccp->cc_magsize != mtp->mt_magsize) {
				mutex_exit(&ccp->cc_lock);
				kmem_cache_free(mtp->mt_cache, emp);
				mutex_enter(&ccp->cc_lock);
				continue;
			}

			/*
			 * We got a magazine of the right size.  Add it to
			 * the depot and try the whole dance again.
			 */
			kmem_depot_free(cp, &cp->cache_empty, emp);
			continue;
		}

		/*
		 * We couldn't allocate an empty magazine,
		 * so fall through to the slab layer.
		 */
		break;
	}
	mutex_exit(&ccp->cc_lock);

	/*
	 * We couldn't free our constructed object to the magazine layer,
	 * so apply its destructor and free it to the slab layer.
	 */
	kmem_slab_free_constructed(cp, buf, B_TRUE);
}

void *
kmem_zalloc(size_t size, int kmflag)
{
	size_t index = (size - 1) >> KMEM_ALIGN_SHIFT;
	void *buf;

	if (index < KMEM_MAXBUF >> KMEM_ALIGN_SHIFT) {
		kmem_cache_t *cp = kmem_alloc_table[index];
		buf = kmem_cache_alloc(cp, kmflag);
		if (buf != NULL) {
			if (cp->cache_flags & KMF_BUFTAG) {
				kmem_buftag_t *btp = KMEM_BUFTAG(cp, buf);
				((uint8_t *)buf)[size] = KMEM_REDZONE_BYTE;
				((uint32_t *)btp)[1] = KMEM_SIZE_ENCODE(size);

				if (cp->cache_flags & KMF_LITE) {
					KMEM_BUFTAG_LITE_ENTER(btp,
					    kmem_lite_count, caller());
				}
			}
			bzero(buf, size);
		}
	} else {
		buf = kmem_alloc(size, kmflag);
		if (buf != NULL)
			bzero(buf, size);
	}
	return (buf);
}

void *
kmem_alloc(size_t size, int kmflag)
{
	size_t index = (size - 1) >> KMEM_ALIGN_SHIFT;
	void *buf;

	if (index < KMEM_MAXBUF >> KMEM_ALIGN_SHIFT) {
		kmem_cache_t *cp = kmem_alloc_table[index];
		buf = kmem_cache_alloc(cp, kmflag);
		if ((cp->cache_flags & KMF_BUFTAG) && buf != NULL) {
			kmem_buftag_t *btp = KMEM_BUFTAG(cp, buf);
			((uint8_t *)buf)[size] = KMEM_REDZONE_BYTE;
			((uint32_t *)btp)[1] = KMEM_SIZE_ENCODE(size);

			if (cp->cache_flags & KMF_LITE) {
				KMEM_BUFTAG_LITE_ENTER(btp, kmem_lite_count,
				    caller());
			}
		}
		return (buf);
	}
	if (size == 0)
		return (NULL);
	buf = vmem_alloc(kmem_oversize_arena, size, kmflag & KM_VMFLAGS);
	if (buf == NULL)
		kmem_log_event(kmem_failure_log, NULL, NULL, (void *)size);
	return (buf);
}

void
kmem_free(void *buf, size_t size)
{
	size_t index = (size - 1) >> KMEM_ALIGN_SHIFT;

	if (index < KMEM_MAXBUF >> KMEM_ALIGN_SHIFT) {
		kmem_cache_t *cp = kmem_alloc_table[index];
		if (cp->cache_flags & KMF_BUFTAG) {
			kmem_buftag_t *btp = KMEM_BUFTAG(cp, buf);
			uint32_t *ip = (uint32_t *)btp;
			if (ip[1] != KMEM_SIZE_ENCODE(size)) {
				if (*(uint64_t *)buf == KMEM_FREE_PATTERN) {
					kmem_error(KMERR_DUPFREE, cp, buf);
					return;
				}
				if (KMEM_SIZE_VALID(ip[1])) {
					ip[0] = KMEM_SIZE_ENCODE(size);
					kmem_error(KMERR_BADSIZE, cp, buf);
				} else {
					kmem_error(KMERR_REDZONE, cp, buf);
				}
				return;
			}
			if (((uint8_t *)buf)[size] != KMEM_REDZONE_BYTE) {
				kmem_error(KMERR_REDZONE, cp, buf);
				return;
			}
			btp->bt_redzone = KMEM_REDZONE_PATTERN;
			if (cp->cache_flags & KMF_LITE) {
				KMEM_BUFTAG_LITE_ENTER(btp, kmem_lite_count,
				    caller());
			}
		}
		kmem_cache_free(cp, buf);
	} else {
		if (buf == NULL && size == 0)
			return;
		vmem_free(kmem_oversize_arena, buf, size);
	}
}

void *
kmem_firewall_va_alloc(vmem_t *vmp, size_t size, int vmflag)
{
	size_t realsize = size + vmp->vm_quantum;
	void *addr;

	/*
	 * Annoying edge case: if 'size' is just shy of ULONG_MAX, adding
	 * vm_quantum will cause integer wraparound.  Check for this, and
	 * blow off the firewall page in this case.  Note that such a
	 * giant allocation (the entire kernel address space) can never
	 * be satisfied, so it will either fail immediately (VM_NOSLEEP)
	 * or sleep forever (VM_SLEEP).  Thus, there is no need for a
	 * corresponding check in kmem_firewall_va_free().
	 */
	if (realsize < size)
		realsize = size;

	/*
	 * While boot still owns resource management, make sure that this
	 * redzone virtual address allocation is properly accounted for in
	 * OBPs "virtual-memory" "available" lists because we're
	 * effectively claiming them for a red zone.  If we don't do this,
	 * the available lists become too fragmented and too large for the
	 * current boot/kernel memory list interface.
	 */
	addr = vmem_alloc(vmp, realsize, vmflag | VM_NEXTFIT);

	if (addr != NULL && kvseg.s_base == NULL && realsize != size)
		(void) boot_virt_alloc((char *)addr + size, vmp->vm_quantum);

	return (addr);
}

void
kmem_firewall_va_free(vmem_t *vmp, void *addr, size_t size)
{
	ASSERT((kvseg.s_base == NULL ?
	    va_to_pfn((char *)addr + size) :
	    hat_getpfnum(kas.a_hat, (caddr_t)addr + size)) == PFN_INVALID);

	vmem_free(vmp, addr, size + vmp->vm_quantum);
}

/*
 * Try to allocate at least `size' bytes of memory without sleeping or
 * panicking. Return actual allocated size in `asize'. If allocation failed,
 * try final allocation with sleep or panic allowed.
 */
void *
kmem_alloc_tryhard(size_t size, size_t *asize, int kmflag)
{
	void *p;

	*asize = P2ROUNDUP(size, KMEM_ALIGN);
	do {
		p = kmem_alloc(*asize, (kmflag | KM_NOSLEEP) & ~KM_PANIC);
		if (p != NULL)
			return (p);
		*asize += KMEM_ALIGN;
	} while (*asize <= PAGESIZE);

	*asize = P2ROUNDUP(size, KMEM_ALIGN);
	return (kmem_alloc(*asize, kmflag));
}

/*
 * Reclaim all unused memory from a cache.
 */
static void
kmem_cache_reap(kmem_cache_t *cp)
{
	ASSERT(taskq_member(kmem_taskq, curthread));

	/*
	 * Ask the cache's owner to free some memory if possible.
	 * The idea is to handle things like the inode cache, which
	 * typically sits on a bunch of memory that it doesn't truly
	 * *need*.  Reclaim policy is entirely up to the owner; this
	 * callback is just an advisory plea for help.
	 */
	if (cp->cache_reclaim != NULL) {
		long delta;

		/*
		 * Reclaimed memory should be reapable (not included in the
		 * depot's working set).
		 */
		delta = cp->cache_full.ml_total;
		cp->cache_reclaim(cp->cache_private);
		delta = cp->cache_full.ml_total - delta;
		if (delta > 0) {
			mutex_enter(&cp->cache_depot_lock);
			cp->cache_full.ml_reaplimit += delta;
			cp->cache_full.ml_min += delta;
			mutex_exit(&cp->cache_depot_lock);
		}
	}

	kmem_depot_ws_reap(cp);

	if (cp->cache_defrag != NULL && !kmem_move_noreap) {
		kmem_cache_defrag(cp);
	}
}

static void
kmem_reap_timeout(void *flag_arg)
{
	uint32_t *flag = (uint32_t *)flag_arg;

	ASSERT(flag == &kmem_reaping || flag == &kmem_reaping_idspace);
	*flag = 0;
}

static void
kmem_reap_done(void *flag)
{
	(void) timeout(kmem_reap_timeout, flag, kmem_reap_interval);
}

static void
kmem_reap_start(void *flag)
{
	ASSERT(flag == &kmem_reaping || flag == &kmem_reaping_idspace);

	if (flag == &kmem_reaping) {
		kmem_cache_applyall(kmem_cache_reap, kmem_taskq, TQ_NOSLEEP);
		/*
		 * if we have segkp under heap, reap segkp cache.
		 */
		if (segkp_fromheap)
			segkp_cache_free();
	}
	else
		kmem_cache_applyall_id(kmem_cache_reap, kmem_taskq, TQ_NOSLEEP);

	/*
	 * We use taskq_dispatch() to schedule a timeout to clear
	 * the flag so that kmem_reap() becomes self-throttling:
	 * we won't reap again until the current reap completes *and*
	 * at least kmem_reap_interval ticks have elapsed.
	 */
	if (!taskq_dispatch(kmem_taskq, kmem_reap_done, flag, TQ_NOSLEEP))
		kmem_reap_done(flag);
}

static void
kmem_reap_common(void *flag_arg)
{
	uint32_t *flag = (uint32_t *)flag_arg;

	if (MUTEX_HELD(&kmem_cache_lock) || kmem_taskq == NULL ||
	    cas32(flag, 0, 1) != 0)
		return;

	/*
	 * It may not be kosher to do memory allocation when a reap is called
	 * is called (for example, if vmem_populate() is in the call chain).
	 * So we start the reap going with a TQ_NOALLOC dispatch.  If the
	 * dispatch fails, we reset the flag, and the next reap will try again.
	 */
	if (!taskq_dispatch(kmem_taskq, kmem_reap_start, flag, TQ_NOALLOC))
		*flag = 0;
}

/*
 * Reclaim all unused memory from all caches.  Called from the VM system
 * when memory gets tight.
 */
void
kmem_reap(void)
{
	kmem_reap_common(&kmem_reaping);
}

/*
 * Reclaim all unused memory from identifier arenas, called when a vmem
 * arena not back by memory is exhausted.  Since reaping memory-backed caches
 * cannot help with identifier exhaustion, we avoid both a large amount of
 * work and unwanted side-effects from reclaim callbacks.
 */
void
kmem_reap_idspace(void)
{
	kmem_reap_common(&kmem_reaping_idspace);
}

/*
 * Purge all magazines from a cache and set its magazine limit to zero.
 * All calls are serialized by the kmem_taskq lock, except for the final
 * call from kmem_cache_destroy().
 */
static void
kmem_cache_magazine_purge(kmem_cache_t *cp)
{
	kmem_cpu_cache_t *ccp;
	kmem_magazine_t *mp, *pmp;
	int rounds, prounds, cpu_seqid;

	ASSERT(!list_link_active(&cp->cache_link) ||
	    taskq_member(kmem_taskq, curthread));
	ASSERT(MUTEX_NOT_HELD(&cp->cache_lock));

	for (cpu_seqid = 0; cpu_seqid < max_ncpus; cpu_seqid++) {
		ccp = &cp->cache_cpu[cpu_seqid];

		mutex_enter(&ccp->cc_lock);
		mp = ccp->cc_loaded;
		pmp = ccp->cc_ploaded;
		rounds = ccp->cc_rounds;
		prounds = ccp->cc_prounds;
		ccp->cc_loaded = NULL;
		ccp->cc_ploaded = NULL;
		ccp->cc_rounds = -1;
		ccp->cc_prounds = -1;
		ccp->cc_magsize = 0;
		mutex_exit(&ccp->cc_lock);

		if (mp)
			kmem_magazine_destroy(cp, mp, rounds);
		if (pmp)
			kmem_magazine_destroy(cp, pmp, prounds);
	}

	/*
	 * Updating the working set statistics twice in a row has the
	 * effect of setting the working set size to zero, so everything
	 * is eligible for reaping.
	 */
	kmem_depot_ws_update(cp);
	kmem_depot_ws_update(cp);

	kmem_depot_ws_reap(cp);
}

/*
 * Enable per-cpu magazines on a cache.
 */
static void
kmem_cache_magazine_enable(kmem_cache_t *cp)
{
	int cpu_seqid;

	if (cp->cache_flags & KMF_NOMAGAZINE)
		return;

	for (cpu_seqid = 0; cpu_seqid < max_ncpus; cpu_seqid++) {
		kmem_cpu_cache_t *ccp = &cp->cache_cpu[cpu_seqid];
		mutex_enter(&ccp->cc_lock);
		ccp->cc_magsize = cp->cache_magtype->mt_magsize;
		mutex_exit(&ccp->cc_lock);
	}

}

/*
 * Reap (almost) everything right now.  See kmem_cache_magazine_purge()
 * for explanation of the back-to-back kmem_depot_ws_update() calls.
 */
void
kmem_cache_reap_now(kmem_cache_t *cp)
{
	ASSERT(list_link_active(&cp->cache_link));

	kmem_depot_ws_update(cp);
	kmem_depot_ws_update(cp);

	(void) taskq_dispatch(kmem_taskq,
	    (task_func_t *)kmem_depot_ws_reap, cp, TQ_SLEEP);
	taskq_wait(kmem_taskq);
}

/*
 * Recompute a cache's magazine size.  The trade-off is that larger magazines
 * provide a higher transfer rate with the depot, while smaller magazines
 * reduce memory consumption.  Magazine resizing is an expensive operation;
 * it should not be done frequently.
 *
 * Changes to the magazine size are serialized by the kmem_taskq lock.
 *
 * Note: at present this only grows the magazine size.  It might be useful
 * to allow shrinkage too.
 */
static void
kmem_cache_magazine_resize(kmem_cache_t *cp)
{
	kmem_magtype_t *mtp = cp->cache_magtype;

	ASSERT(taskq_member(kmem_taskq, curthread));

	if (cp->cache_chunksize < mtp->mt_maxbuf) {
		kmem_cache_magazine_purge(cp);
		mutex_enter(&cp->cache_depot_lock);
		cp->cache_magtype = ++mtp;
		cp->cache_depot_contention_prev =
		    cp->cache_depot_contention + INT_MAX;
		mutex_exit(&cp->cache_depot_lock);
		kmem_cache_magazine_enable(cp);
	}
}

/*
 * Rescale a cache's hash table, so that the table size is roughly the
 * cache size.  We want the average lookup time to be extremely small.
 */
static void
kmem_hash_rescale(kmem_cache_t *cp)
{
	kmem_bufctl_t **old_table, **new_table, *bcp;
	size_t old_size, new_size, h;

	ASSERT(taskq_member(kmem_taskq, curthread));

	new_size = MAX(KMEM_HASH_INITIAL,
	    1 << (highbit(3 * cp->cache_buftotal + 4) - 2));
	old_size = cp->cache_hash_mask + 1;

	if ((old_size >> 1) <= new_size && new_size <= (old_size << 1))
		return;

	new_table = vmem_alloc(kmem_hash_arena, new_size * sizeof (void *),
	    VM_NOSLEEP);
	if (new_table == NULL)
		return;
	bzero(new_table, new_size * sizeof (void *));

	mutex_enter(&cp->cache_lock);

	old_size = cp->cache_hash_mask + 1;
	old_table = cp->cache_hash_table;

	cp->cache_hash_mask = new_size - 1;
	cp->cache_hash_table = new_table;
	cp->cache_rescale++;

	for (h = 0; h < old_size; h++) {
		bcp = old_table[h];
		while (bcp != NULL) {
			void *addr = bcp->bc_addr;
			kmem_bufctl_t *next_bcp = bcp->bc_next;
			kmem_bufctl_t **hash_bucket = KMEM_HASH(cp, addr);
			bcp->bc_next = *hash_bucket;
			*hash_bucket = bcp;
			bcp = next_bcp;
		}
	}

	mutex_exit(&cp->cache_lock);

	vmem_free(kmem_hash_arena, old_table, old_size * sizeof (void *));
}

/*
 * Perform periodic maintenance on a cache: hash rescaling, depot working-set
 * update, magazine resizing, and slab consolidation.
 */
static void
kmem_cache_update(kmem_cache_t *cp)
{
	int need_hash_rescale = 0;
	int need_magazine_resize = 0;

	ASSERT(MUTEX_HELD(&kmem_cache_lock));

	/*
	 * If the cache has become much larger or smaller than its hash table,
	 * fire off a request to rescale the hash table.
	 */
	mutex_enter(&cp->cache_lock);

	if ((cp->cache_flags & KMF_HASH) &&
	    (cp->cache_buftotal > (cp->cache_hash_mask << 1) ||
	    (cp->cache_buftotal < (cp->cache_hash_mask >> 1) &&
	    cp->cache_hash_mask > KMEM_HASH_INITIAL)))
		need_hash_rescale = 1;

	mutex_exit(&cp->cache_lock);

	/*
	 * Update the depot working set statistics.
	 */
	kmem_depot_ws_update(cp);

	/*
	 * If there's a lot of contention in the depot,
	 * increase the magazine size.
	 */
	mutex_enter(&cp->cache_depot_lock);

	if (cp->cache_chunksize < cp->cache_magtype->mt_maxbuf &&
	    (int)(cp->cache_depot_contention -
	    cp->cache_depot_contention_prev) > kmem_depot_contention)
		need_magazine_resize = 1;

	cp->cache_depot_contention_prev = cp->cache_depot_contention;

	mutex_exit(&cp->cache_depot_lock);

	if (need_hash_rescale)
		(void) taskq_dispatch(kmem_taskq,
		    (task_func_t *)kmem_hash_rescale, cp, TQ_NOSLEEP);

	if (need_magazine_resize)
		(void) taskq_dispatch(kmem_taskq,
		    (task_func_t *)kmem_cache_magazine_resize, cp, TQ_NOSLEEP);

	if (cp->cache_defrag != NULL)
		(void) taskq_dispatch(kmem_taskq,
		    (task_func_t *)kmem_cache_scan, cp, TQ_NOSLEEP);
}

static void
kmem_update_timeout(void *dummy)
{
	static void kmem_update(void *);

	(void) timeout(kmem_update, dummy, kmem_reap_interval);
}

static void
kmem_update(void *dummy)
{
	kmem_cache_applyall(kmem_cache_update, NULL, TQ_NOSLEEP);

	/*
	 * We use taskq_dispatch() to reschedule the timeout so that
	 * kmem_update() becomes self-throttling: it won't schedule
	 * new tasks until all previous tasks have completed.
	 */
	if (!taskq_dispatch(kmem_taskq, kmem_update_timeout, dummy, TQ_NOSLEEP))
		kmem_update_timeout(NULL);
}

static int
kmem_cache_kstat_update(kstat_t *ksp, int rw)
{
	struct kmem_cache_kstat *kmcp = &kmem_cache_kstat;
	kmem_cache_t *cp = ksp->ks_private;
	uint64_t cpu_buf_avail;
	uint64_t buf_avail = 0;
	int cpu_seqid;

	ASSERT(MUTEX_HELD(&kmem_cache_kstat_lock));

	if (rw == KSTAT_WRITE)
		return (EACCES);

	mutex_enter(&cp->cache_lock);

	kmcp->kmc_alloc_fail.value.ui64		= cp->cache_alloc_fail;
	kmcp->kmc_alloc.value.ui64		= cp->cache_slab_alloc;
	kmcp->kmc_free.value.ui64		= cp->cache_slab_free;
	kmcp->kmc_slab_alloc.value.ui64		= cp->cache_slab_alloc;
	kmcp->kmc_slab_free.value.ui64		= cp->cache_slab_free;

	for (cpu_seqid = 0; cpu_seqid < max_ncpus; cpu_seqid++) {
		kmem_cpu_cache_t *ccp = &cp->cache_cpu[cpu_seqid];

		mutex_enter(&ccp->cc_lock);

		cpu_buf_avail = 0;
		if (ccp->cc_rounds > 0)
			cpu_buf_avail += ccp->cc_rounds;
		if (ccp->cc_prounds > 0)
			cpu_buf_avail += ccp->cc_prounds;

		kmcp->kmc_alloc.value.ui64	+= ccp->cc_alloc;
		kmcp->kmc_free.value.ui64	+= ccp->cc_free;
		buf_avail			+= cpu_buf_avail;

		mutex_exit(&ccp->cc_lock);
	}

	mutex_enter(&cp->cache_depot_lock);

	kmcp->kmc_depot_alloc.value.ui64	= cp->cache_full.ml_alloc;
	kmcp->kmc_depot_free.value.ui64		= cp->cache_empty.ml_alloc;
	kmcp->kmc_depot_contention.value.ui64	= cp->cache_depot_contention;
	kmcp->kmc_full_magazines.value.ui64	= cp->cache_full.ml_total;
	kmcp->kmc_empty_magazines.value.ui64	= cp->cache_empty.ml_total;
	kmcp->kmc_magazine_size.value.ui64	=
	    (cp->cache_flags & KMF_NOMAGAZINE) ?
	    0 : cp->cache_magtype->mt_magsize;

	kmcp->kmc_alloc.value.ui64		+= cp->cache_full.ml_alloc;
	kmcp->kmc_free.value.ui64		+= cp->cache_empty.ml_alloc;
	buf_avail += cp->cache_full.ml_total * cp->cache_magtype->mt_magsize;

	mutex_exit(&cp->cache_depot_lock);

	kmcp->kmc_buf_size.value.ui64	= cp->cache_bufsize;
	kmcp->kmc_align.value.ui64	= cp->cache_align;
	kmcp->kmc_chunk_size.value.ui64	= cp->cache_chunksize;
	kmcp->kmc_slab_size.value.ui64	= cp->cache_slabsize;
	kmcp->kmc_buf_constructed.value.ui64 = buf_avail;
	buf_avail += cp->cache_bufslab;
	kmcp->kmc_buf_avail.value.ui64	= buf_avail;
	kmcp->kmc_buf_inuse.value.ui64	= cp->cache_buftotal - buf_avail;
	kmcp->kmc_buf_total.value.ui64	= cp->cache_buftotal;
	kmcp->kmc_buf_max.value.ui64	= cp->cache_bufmax;
	kmcp->kmc_slab_create.value.ui64	= cp->cache_slab_create;
	kmcp->kmc_slab_destroy.value.ui64	= cp->cache_slab_destroy;
	kmcp->kmc_hash_size.value.ui64	= (cp->cache_flags & KMF_HASH) ?
	    cp->cache_hash_mask + 1 : 0;
	kmcp->kmc_hash_lookup_depth.value.ui64	= cp->cache_lookup_depth;
	kmcp->kmc_hash_rescale.value.ui64	= cp->cache_rescale;
	kmcp->kmc_vmem_source.value.ui64	= cp->cache_arena->vm_id;

	if (cp->cache_defrag == NULL) {
		kmcp->kmc_move_callbacks.value.ui64	= 0;
		kmcp->kmc_move_yes.value.ui64		= 0;
		kmcp->kmc_move_no.value.ui64		= 0;
		kmcp->kmc_move_later.value.ui64		= 0;
		kmcp->kmc_move_dont_need.value.ui64	= 0;
		kmcp->kmc_move_dont_know.value.ui64	= 0;
		kmcp->kmc_move_hunt_found.value.ui64	= 0;
	} else {
		kmem_defrag_t *kd = cp->cache_defrag;
		kmcp->kmc_move_callbacks.value.ui64	= kd->kmd_callbacks;
		kmcp->kmc_move_yes.value.ui64		= kd->kmd_yes;
		kmcp->kmc_move_no.value.ui64		= kd->kmd_no;
		kmcp->kmc_move_later.value.ui64		= kd->kmd_later;
		kmcp->kmc_move_dont_need.value.ui64	= kd->kmd_dont_need;
		kmcp->kmc_move_dont_know.value.ui64	= kd->kmd_dont_know;
		kmcp->kmc_move_hunt_found.value.ui64	= kd->kmd_hunt_found;
	}

	mutex_exit(&cp->cache_lock);
	return (0);
}

/*
 * Return a named statistic about a particular cache.
 * This shouldn't be called very often, so it's currently designed for
 * simplicity (leverages existing kstat support) rather than efficiency.
 */
uint64_t
kmem_cache_stat(kmem_cache_t *cp, char *name)
{
	int i;
	kstat_t *ksp = cp->cache_kstat;
	kstat_named_t *knp = (kstat_named_t *)&kmem_cache_kstat;
	uint64_t value = 0;

	if (ksp != NULL) {
		mutex_enter(&kmem_cache_kstat_lock);
		(void) kmem_cache_kstat_update(ksp, KSTAT_READ);
		for (i = 0; i < ksp->ks_ndata; i++) {
			if (strcmp(knp[i].name, name) == 0) {
				value = knp[i].value.ui64;
				break;
			}
		}
		mutex_exit(&kmem_cache_kstat_lock);
	}
	return (value);
}

/*
 * Return an estimate of currently available kernel heap memory.
 * On 32-bit systems, physical memory may exceed virtual memory,
 * we just truncate the result at 1GB.
 */
size_t
kmem_avail(void)
{
	spgcnt_t rmem = availrmem - tune.t_minarmem;
	spgcnt_t fmem = freemem - minfree;

	return ((size_t)ptob(MIN(MAX(MIN(rmem, fmem), 0),
	    1 << (30 - PAGESHIFT))));
}

/*
 * Return the maximum amount of memory that is (in theory) allocatable
 * from the heap. This may be used as an estimate only since there
 * is no guarentee this space will still be available when an allocation
 * request is made, nor that the space may be allocated in one big request
 * due to kernel heap fragmentation.
 */
size_t
kmem_maxavail(void)
{
	spgcnt_t pmem = availrmem - tune.t_minarmem;
	spgcnt_t vmem = btop(vmem_size(heap_arena, VMEM_FREE));

	return ((size_t)ptob(MAX(MIN(pmem, vmem), 0)));
}

/*
 * Indicate whether memory-intensive kmem debugging is enabled.
 */
int
kmem_debugging(void)
{
	return (kmem_flags & (KMF_AUDIT | KMF_REDZONE));
}

/* binning function, sorts finely at the two extremes */
#define	KMEM_PARTIAL_SLAB_WEIGHT(sp, binshift)				\
	((((sp)->slab_refcnt <= (binshift)) ||				\
	    (((sp)->slab_chunks - (sp)->slab_refcnt) <= (binshift)))	\
	    ? -(sp)->slab_refcnt					\
	    : -((binshift) + ((sp)->slab_refcnt >> (binshift))))

/*
 * Minimizing the number of partial slabs on the freelist minimizes
 * fragmentation (the ratio of unused buffers held by the slab layer). There are
 * two ways to get a slab off of the freelist: 1) free all the buffers on the
 * slab, and 2) allocate all the buffers on the slab. It follows that we want
 * the most-used slabs at the front of the list where they have the best chance
 * of being completely allocated, and the least-used slabs at a safe distance
 * from the front to improve the odds that the few remaining buffers will all be
 * freed before another allocation can tie up the slab. For that reason a slab
 * with a higher slab_refcnt sorts less than than a slab with a lower
 * slab_refcnt.
 *
 * However, if a slab has at least one buffer that is deemed unfreeable, we
 * would rather have that slab at the front of the list regardless of
 * slab_refcnt, since even one unfreeable buffer makes the entire slab
 * unfreeable. If the client returns KMEM_CBRC_NO in response to a cache_move()
 * callback, the slab is marked unfreeable for as long as it remains on the
 * freelist.
 */
static int
kmem_partial_slab_cmp(const void *p0, const void *p1)
{
	const kmem_cache_t *cp;
	const kmem_slab_t *s0 = p0;
	const kmem_slab_t *s1 = p1;
	int w0, w1;
	size_t binshift;

	ASSERT(KMEM_SLAB_IS_PARTIAL(s0));
	ASSERT(KMEM_SLAB_IS_PARTIAL(s1));
	ASSERT(s0->slab_cache == s1->slab_cache);
	cp = s1->slab_cache;
	ASSERT(MUTEX_HELD(&cp->cache_lock));
	binshift = cp->cache_partial_binshift;

	/* weight of first slab */
	w0 = KMEM_PARTIAL_SLAB_WEIGHT(s0, binshift);
	if (s0->slab_flags & KMEM_SLAB_NOMOVE) {
		w0 -= cp->cache_maxchunks;
	}

	/* weight of second slab */
	w1 = KMEM_PARTIAL_SLAB_WEIGHT(s1, binshift);
	if (s1->slab_flags & KMEM_SLAB_NOMOVE) {
		w1 -= cp->cache_maxchunks;
	}

	if (w0 < w1)
		return (-1);
	if (w0 > w1)
		return (1);

	/* compare pointer values */
	if ((uintptr_t)s0 < (uintptr_t)s1)
		return (-1);
	if ((uintptr_t)s0 > (uintptr_t)s1)
		return (1);

	return (0);
}

/*
 * It must be valid to call the destructor (if any) on a newly created object.
 * That is, the constructor (if any) must leave the object in a valid state for
 * the destructor.
 */
kmem_cache_t *
kmem_cache_create(
	char *name,		/* descriptive name for this cache */
	size_t bufsize,		/* size of the objects it manages */
	size_t align,		/* required object alignment */
	int (*constructor)(void *, void *, int), /* object constructor */
	void (*destructor)(void *, void *),	/* object destructor */
	void (*reclaim)(void *), /* memory reclaim callback */
	void *private,		/* pass-thru arg for constr/destr/reclaim */
	vmem_t *vmp,		/* vmem source for slab allocation */
	int cflags)		/* cache creation flags */
{
	int cpu_seqid;
	size_t chunksize;
	kmem_cache_t *cp;
	kmem_magtype_t *mtp;
	size_t csize = KMEM_CACHE_SIZE(max_ncpus);

#ifdef	DEBUG
	/*
	 * Cache names should conform to the rules for valid C identifiers
	 */
	if (!strident_valid(name)) {
		cmn_err(CE_CONT,
		    "kmem_cache_create: '%s' is an invalid cache name\n"
		    "cache names must conform to the rules for "
		    "C identifiers\n", name);
	}
#endif	/* DEBUG */

	if (vmp == NULL)
		vmp = kmem_default_arena;

	/*
	 * If this kmem cache has an identifier vmem arena as its source, mark
	 * it such to allow kmem_reap_idspace().
	 */
	ASSERT(!(cflags & KMC_IDENTIFIER));   /* consumer should not set this */
	if (vmp->vm_cflags & VMC_IDENTIFIER)
		cflags |= KMC_IDENTIFIER;

	/*
	 * Get a kmem_cache structure.  We arrange that cp->cache_cpu[]
	 * is aligned on a KMEM_CPU_CACHE_SIZE boundary to prevent
	 * false sharing of per-CPU data.
	 */
	cp = vmem_xalloc(kmem_cache_arena, csize, KMEM_CPU_CACHE_SIZE,
	    P2NPHASE(csize, KMEM_CPU_CACHE_SIZE), 0, NULL, NULL, VM_SLEEP);
	bzero(cp, csize);
	list_link_init(&cp->cache_link);

	if (align == 0)
		align = KMEM_ALIGN;

	/*
	 * If we're not at least KMEM_ALIGN aligned, we can't use free
	 * memory to hold bufctl information (because we can't safely
	 * perform word loads and stores on it).
	 */
	if (align < KMEM_ALIGN)
		cflags |= KMC_NOTOUCH;

	if ((align & (align - 1)) != 0 || align > vmp->vm_quantum)
		panic("kmem_cache_create: bad alignment %lu", align);

	mutex_enter(&kmem_flags_lock);
	if (kmem_flags & KMF_RANDOMIZE)
		kmem_flags = (((kmem_flags | ~KMF_RANDOM) + 1) & KMF_RANDOM) |
		    KMF_RANDOMIZE;
	cp->cache_flags = (kmem_flags | cflags) & KMF_DEBUG;
	mutex_exit(&kmem_flags_lock);

	/*
	 * Make sure all the various flags are reasonable.
	 */
	ASSERT(!(cflags & KMC_NOHASH) || !(cflags & KMC_NOTOUCH));

	if (cp->cache_flags & KMF_LITE) {
		if (bufsize >= kmem_lite_minsize &&
		    align <= kmem_lite_maxalign &&
		    P2PHASE(bufsize, kmem_lite_maxalign) != 0) {
			cp->cache_flags |= KMF_BUFTAG;
			cp->cache_flags &= ~(KMF_AUDIT | KMF_FIREWALL);
		} else {
			cp->cache_flags &= ~KMF_DEBUG;
		}
	}

	if (cp->cache_flags & KMF_DEADBEEF)
		cp->cache_flags |= KMF_REDZONE;

	if ((cflags & KMC_QCACHE) && (cp->cache_flags & KMF_AUDIT))
		cp->cache_flags |= KMF_NOMAGAZINE;

	if (cflags & KMC_NODEBUG)
		cp->cache_flags &= ~KMF_DEBUG;

	if (cflags & KMC_NOTOUCH)
		cp->cache_flags &= ~KMF_TOUCH;

	if (cflags & KMC_NOHASH)
		cp->cache_flags &= ~(KMF_AUDIT | KMF_FIREWALL);

	if (cflags & KMC_NOMAGAZINE)
		cp->cache_flags |= KMF_NOMAGAZINE;

	if ((cp->cache_flags & KMF_AUDIT) && !(cflags & KMC_NOTOUCH))
		cp->cache_flags |= KMF_REDZONE;

	if (!(cp->cache_flags & KMF_AUDIT))
		cp->cache_flags &= ~KMF_CONTENTS;

	if ((cp->cache_flags & KMF_BUFTAG) && bufsize >= kmem_minfirewall &&
	    !(cp->cache_flags & KMF_LITE) && !(cflags & KMC_NOHASH))
		cp->cache_flags |= KMF_FIREWALL;

	if (vmp != kmem_default_arena || kmem_firewall_arena == NULL)
		cp->cache_flags &= ~KMF_FIREWALL;

	if (cp->cache_flags & KMF_FIREWALL) {
		cp->cache_flags &= ~KMF_BUFTAG;
		cp->cache_flags |= KMF_NOMAGAZINE;
		ASSERT(vmp == kmem_default_arena);
		vmp = kmem_firewall_arena;
	}

	/*
	 * Set cache properties.
	 */
	(void) strncpy(cp->cache_name, name, KMEM_CACHE_NAMELEN);
	strident_canon(cp->cache_name, KMEM_CACHE_NAMELEN + 1);
	cp->cache_bufsize = bufsize;
	cp->cache_align = align;
	cp->cache_constructor = constructor;
	cp->cache_destructor = destructor;
	cp->cache_reclaim = reclaim;
	cp->cache_private = private;
	cp->cache_arena = vmp;
	cp->cache_cflags = cflags;

	/*
	 * Determine the chunk size.
	 */
	chunksize = bufsize;

	if (align >= KMEM_ALIGN) {
		chunksize = P2ROUNDUP(chunksize, KMEM_ALIGN);
		cp->cache_bufctl = chunksize - KMEM_ALIGN;
	}

	if (cp->cache_flags & KMF_BUFTAG) {
		cp->cache_bufctl = chunksize;
		cp->cache_buftag = chunksize;
		if (cp->cache_flags & KMF_LITE)
			chunksize += KMEM_BUFTAG_LITE_SIZE(kmem_lite_count);
		else
			chunksize += sizeof (kmem_buftag_t);
	}

	if (cp->cache_flags & KMF_DEADBEEF) {
		cp->cache_verify = MIN(cp->cache_buftag, kmem_maxverify);
		if (cp->cache_flags & KMF_LITE)
			cp->cache_verify = sizeof (uint64_t);
	}

	cp->cache_contents = MIN(cp->cache_bufctl, kmem_content_maxsave);

	cp->cache_chunksize = chunksize = P2ROUNDUP(chunksize, align);

	/*
	 * Now that we know the chunk size, determine the optimal slab size.
	 */
	if (vmp == kmem_firewall_arena) {
		cp->cache_slabsize = P2ROUNDUP(chunksize, vmp->vm_quantum);
		cp->cache_mincolor = cp->cache_slabsize - chunksize;
		cp->cache_maxcolor = cp->cache_mincolor;
		cp->cache_flags |= KMF_HASH;
		ASSERT(!(cp->cache_flags & KMF_BUFTAG));
	} else if ((cflags & KMC_NOHASH) || (!(cflags & KMC_NOTOUCH) &&
	    !(cp->cache_flags & KMF_AUDIT) &&
	    chunksize < vmp->vm_quantum / KMEM_VOID_FRACTION)) {
		cp->cache_slabsize = vmp->vm_quantum;
		cp->cache_mincolor = 0;
		cp->cache_maxcolor =
		    (cp->cache_slabsize - sizeof (kmem_slab_t)) % chunksize;
		ASSERT(chunksize + sizeof (kmem_slab_t) <= cp->cache_slabsize);
		ASSERT(!(cp->cache_flags & KMF_AUDIT));
	} else {
		size_t chunks, bestfit, waste, slabsize;
		size_t minwaste = LONG_MAX;

		for (chunks = 1; chunks <= KMEM_VOID_FRACTION; chunks++) {
			slabsize = P2ROUNDUP(chunksize * chunks,
			    vmp->vm_quantum);
			chunks = slabsize / chunksize;
			waste = (slabsize % chunksize) / chunks;
			if (waste < minwaste) {
				minwaste = waste;
				bestfit = slabsize;
			}
		}
		if (cflags & KMC_QCACHE)
			bestfit = VMEM_QCACHE_SLABSIZE(vmp->vm_qcache_max);
		cp->cache_slabsize = bestfit;
		cp->cache_mincolor = 0;
		cp->cache_maxcolor = bestfit % chunksize;
		cp->cache_flags |= KMF_HASH;
	}

	cp->cache_maxchunks = (cp->cache_slabsize / cp->cache_chunksize);
	cp->cache_partial_binshift = highbit(cp->cache_maxchunks / 16) + 1;

	if (cp->cache_flags & KMF_HASH) {
		ASSERT(!(cflags & KMC_NOHASH));
		cp->cache_bufctl_cache = (cp->cache_flags & KMF_AUDIT) ?
		    kmem_bufctl_audit_cache : kmem_bufctl_cache;
	}

	if (cp->cache_maxcolor >= vmp->vm_quantum)
		cp->cache_maxcolor = vmp->vm_quantum - 1;

	cp->cache_color = cp->cache_mincolor;

	/*
	 * Initialize the rest of the slab layer.
	 */
	mutex_init(&cp->cache_lock, NULL, MUTEX_DEFAULT, NULL);

	avl_create(&cp->cache_partial_slabs, kmem_partial_slab_cmp,
	    sizeof (kmem_slab_t), offsetof(kmem_slab_t, slab_link));
	/* LINTED: E_TRUE_LOGICAL_EXPR */
	ASSERT(sizeof (list_node_t) <= sizeof (avl_node_t));
	/* reuse partial slab AVL linkage for complete slab list linkage */
	list_create(&cp->cache_complete_slabs,
	    sizeof (kmem_slab_t), offsetof(kmem_slab_t, slab_link));

	if (cp->cache_flags & KMF_HASH) {
		cp->cache_hash_table = vmem_alloc(kmem_hash_arena,
		    KMEM_HASH_INITIAL * sizeof (void *), VM_SLEEP);
		bzero(cp->cache_hash_table,
		    KMEM_HASH_INITIAL * sizeof (void *));
		cp->cache_hash_mask = KMEM_HASH_INITIAL - 1;
		cp->cache_hash_shift = highbit((ulong_t)chunksize) - 1;
	}

	/*
	 * Initialize the depot.
	 */
	mutex_init(&cp->cache_depot_lock, NULL, MUTEX_DEFAULT, NULL);

	for (mtp = kmem_magtype; chunksize <= mtp->mt_minbuf; mtp++)
		continue;

	cp->cache_magtype = mtp;

	/*
	 * Initialize the CPU layer.
	 */
	for (cpu_seqid = 0; cpu_seqid < max_ncpus; cpu_seqid++) {
		kmem_cpu_cache_t *ccp = &cp->cache_cpu[cpu_seqid];
		mutex_init(&ccp->cc_lock, NULL, MUTEX_DEFAULT, NULL);
		ccp->cc_flags = cp->cache_flags;
		ccp->cc_rounds = -1;
		ccp->cc_prounds = -1;
	}

	/*
	 * Create the cache's kstats.
	 */
	if ((cp->cache_kstat = kstat_create("unix", 0, cp->cache_name,
	    "kmem_cache", KSTAT_TYPE_NAMED,
	    sizeof (kmem_cache_kstat) / sizeof (kstat_named_t),
	    KSTAT_FLAG_VIRTUAL)) != NULL) {
		cp->cache_kstat->ks_data = &kmem_cache_kstat;
		cp->cache_kstat->ks_update = kmem_cache_kstat_update;
		cp->cache_kstat->ks_private = cp;
		cp->cache_kstat->ks_lock = &kmem_cache_kstat_lock;
		kstat_install(cp->cache_kstat);
	}

	/*
	 * Add the cache to the global list.  This makes it visible
	 * to kmem_update(), so the cache must be ready for business.
	 */
	mutex_enter(&kmem_cache_lock);
	list_insert_tail(&kmem_caches, cp);
	mutex_exit(&kmem_cache_lock);

	if (kmem_ready)
		kmem_cache_magazine_enable(cp);

	return (cp);
}

static int
kmem_move_cmp(const void *buf, const void *p)
{
	const kmem_move_t *kmm = p;
	uintptr_t v1 = (uintptr_t)buf;
	uintptr_t v2 = (uintptr_t)kmm->kmm_from_buf;
	return (v1 < v2 ? -1 : (v1 > v2 ? 1 : 0));
}

static void
kmem_reset_reclaim_threshold(kmem_defrag_t *kmd)
{
	kmd->kmd_reclaim_numer = 1;
}

/*
 * Initially, when choosing candidate slabs for buffers to move, we want to be
 * very selective and take only slabs that are less than
 * (1 / KMEM_VOID_FRACTION) allocated. If we have difficulty finding candidate
 * slabs, then we raise the allocation ceiling incrementally. The reclaim
 * threshold is reset to (1 / KMEM_VOID_FRACTION) as soon as the cache is no
 * longer fragmented.
 */
static void
kmem_adjust_reclaim_threshold(kmem_defrag_t *kmd, int direction)
{
	if (direction > 0) {
		/* make it easier to find a candidate slab */
		if (kmd->kmd_reclaim_numer < (KMEM_VOID_FRACTION - 1)) {
			kmd->kmd_reclaim_numer++;
		}
	} else {
		/* be more selective */
		if (kmd->kmd_reclaim_numer > 1) {
			kmd->kmd_reclaim_numer--;
		}
	}
}

void
kmem_cache_set_move(kmem_cache_t *cp,
    kmem_cbrc_t (*move)(void *, void *, size_t, void *))
{
	kmem_defrag_t *defrag;

	ASSERT(move != NULL);
	/*
	 * The consolidator does not support NOTOUCH caches because kmem cannot
	 * initialize their slabs with the 0xbaddcafe memory pattern, which sets
	 * a low order bit usable by clients to distinguish uninitialized memory
	 * from known objects (see kmem_slab_create).
	 */
	ASSERT(!(cp->cache_cflags & KMC_NOTOUCH));
	ASSERT(!(cp->cache_cflags & KMC_IDENTIFIER));

	/*
	 * We should not be holding anyone's cache lock when calling
	 * kmem_cache_alloc(), so allocate in all cases before acquiring the
	 * lock.
	 */
	defrag = kmem_cache_alloc(kmem_defrag_cache, KM_SLEEP);

	mutex_enter(&cp->cache_lock);

	if (KMEM_IS_MOVABLE(cp)) {
		if (cp->cache_move == NULL) {
			ASSERT(cp->cache_slab_alloc == 0);

			cp->cache_defrag = defrag;
			defrag = NULL; /* nothing to free */
			bzero(cp->cache_defrag, sizeof (kmem_defrag_t));
			avl_create(&cp->cache_defrag->kmd_moves_pending,
			    kmem_move_cmp, sizeof (kmem_move_t),
			    offsetof(kmem_move_t, kmm_entry));
			/* LINTED: E_TRUE_LOGICAL_EXPR */
			ASSERT(sizeof (list_node_t) <= sizeof (avl_node_t));
			/* reuse the slab's AVL linkage for deadlist linkage */
			list_create(&cp->cache_defrag->kmd_deadlist,
			    sizeof (kmem_slab_t),
			    offsetof(kmem_slab_t, slab_link));
			kmem_reset_reclaim_threshold(cp->cache_defrag);
		}
		cp->cache_move = move;
	}

	mutex_exit(&cp->cache_lock);

	if (defrag != NULL) {
		kmem_cache_free(kmem_defrag_cache, defrag); /* unused */
	}
}

void
kmem_cache_destroy(kmem_cache_t *cp)
{
	int cpu_seqid;

	/*
	 * Remove the cache from the global cache list so that no one else
	 * can schedule tasks on its behalf, wait for any pending tasks to
	 * complete, purge the cache, and then destroy it.
	 */
	mutex_enter(&kmem_cache_lock);
	list_remove(&kmem_caches, cp);
	mutex_exit(&kmem_cache_lock);

	if (kmem_taskq != NULL)
		taskq_wait(kmem_taskq);
	if (kmem_move_taskq != NULL)
		taskq_wait(kmem_move_taskq);

	kmem_cache_magazine_purge(cp);

	mutex_enter(&cp->cache_lock);
	if (cp->cache_buftotal != 0)
		cmn_err(CE_WARN, "kmem_cache_destroy: '%s' (%p) not empty",
		    cp->cache_name, (void *)cp);
	if (cp->cache_defrag != NULL) {
		avl_destroy(&cp->cache_defrag->kmd_moves_pending);
		list_destroy(&cp->cache_defrag->kmd_deadlist);
		kmem_cache_free(kmem_defrag_cache, cp->cache_defrag);
		cp->cache_defrag = NULL;
	}
	/*
	 * The cache is now dead.  There should be no further activity.  We
	 * enforce this by setting land mines in the constructor, destructor,
	 * reclaim, and move routines that induce a kernel text fault if
	 * invoked.
	 */
	cp->cache_constructor = (int (*)(void *, void *, int))1;
	cp->cache_destructor = (void (*)(void *, void *))2;
	cp->cache_reclaim = (void (*)(void *))3;
	cp->cache_move = (kmem_cbrc_t (*)(void *, void *, size_t, void *))4;
	mutex_exit(&cp->cache_lock);

	kstat_delete(cp->cache_kstat);

	if (cp->cache_hash_table != NULL)
		vmem_free(kmem_hash_arena, cp->cache_hash_table,
		    (cp->cache_hash_mask + 1) * sizeof (void *));

	for (cpu_seqid = 0; cpu_seqid < max_ncpus; cpu_seqid++)
		mutex_destroy(&cp->cache_cpu[cpu_seqid].cc_lock);

	mutex_destroy(&cp->cache_depot_lock);
	mutex_destroy(&cp->cache_lock);

	vmem_free(kmem_cache_arena, cp, KMEM_CACHE_SIZE(max_ncpus));
}

/*ARGSUSED*/
static int
kmem_cpu_setup(cpu_setup_t what, int id, void *arg)
{
	ASSERT(MUTEX_HELD(&cpu_lock));
	if (what == CPU_UNCONFIG) {
		kmem_cache_applyall(kmem_cache_magazine_purge,
		    kmem_taskq, TQ_SLEEP);
		kmem_cache_applyall(kmem_cache_magazine_enable,
		    kmem_taskq, TQ_SLEEP);
	}
	return (0);
}

static void
kmem_cache_init(int pass, int use_large_pages)
{
	int i;
	size_t size;
	kmem_cache_t *cp;
	kmem_magtype_t *mtp;
	char name[KMEM_CACHE_NAMELEN + 1];

	for (i = 0; i < sizeof (kmem_magtype) / sizeof (*mtp); i++) {
		mtp = &kmem_magtype[i];
		(void) sprintf(name, "kmem_magazine_%d", mtp->mt_magsize);
		mtp->mt_cache = kmem_cache_create(name,
		    (mtp->mt_magsize + 1) * sizeof (void *),
		    mtp->mt_align, NULL, NULL, NULL, NULL,
		    kmem_msb_arena, KMC_NOHASH);
	}

	kmem_slab_cache = kmem_cache_create("kmem_slab_cache",
	    sizeof (kmem_slab_t), 0, NULL, NULL, NULL, NULL,
	    kmem_msb_arena, KMC_NOHASH);

	kmem_bufctl_cache = kmem_cache_create("kmem_bufctl_cache",
	    sizeof (kmem_bufctl_t), 0, NULL, NULL, NULL, NULL,
	    kmem_msb_arena, KMC_NOHASH);

	kmem_bufctl_audit_cache = kmem_cache_create("kmem_bufctl_audit_cache",
	    sizeof (kmem_bufctl_audit_t), 0, NULL, NULL, NULL, NULL,
	    kmem_msb_arena, KMC_NOHASH);

	if (pass == 2) {
		kmem_va_arena = vmem_create("kmem_va",
		    NULL, 0, PAGESIZE,
		    vmem_alloc, vmem_free, heap_arena,
		    8 * PAGESIZE, VM_SLEEP);

		if (use_large_pages) {
			kmem_default_arena = vmem_xcreate("kmem_default",
			    NULL, 0, PAGESIZE,
			    segkmem_alloc_lp, segkmem_free_lp, kmem_va_arena,
			    0, VM_SLEEP);
		} else {
			kmem_default_arena = vmem_create("kmem_default",
			    NULL, 0, PAGESIZE,
			    segkmem_alloc, segkmem_free, kmem_va_arena,
			    0, VM_SLEEP);
		}
	} else {
		/*
		 * During the first pass, the kmem_alloc_* caches
		 * are treated as metadata.
		 */
		kmem_default_arena = kmem_msb_arena;
	}

	/*
	 * Set up the default caches to back kmem_alloc()
	 */
	size = KMEM_ALIGN;
	for (i = 0; i < sizeof (kmem_alloc_sizes) / sizeof (int); i++) {
		size_t align = KMEM_ALIGN;
		size_t cache_size = kmem_alloc_sizes[i];
		/*
		 * If they allocate a multiple of the coherency granularity,
		 * they get a coherency-granularity-aligned address.
		 */
		if (IS_P2ALIGNED(cache_size, 64))
			align = 64;
		if (IS_P2ALIGNED(cache_size, PAGESIZE))
			align = PAGESIZE;
		(void) sprintf(name, "kmem_alloc_%lu", cache_size);
		cp = kmem_cache_create(name, cache_size, align,
		    NULL, NULL, NULL, NULL, NULL, KMC_KMEM_ALLOC);
		while (size <= cache_size) {
			kmem_alloc_table[(size - 1) >> KMEM_ALIGN_SHIFT] = cp;
			size += KMEM_ALIGN;
		}
	}
}

void
kmem_init(void)
{
	kmem_cache_t *cp;
	int old_kmem_flags = kmem_flags;
	int use_large_pages = 0;
	size_t maxverify, minfirewall;

	kstat_init();

	/*
	 * Small-memory systems (< 24 MB) can't handle kmem_flags overhead.
	 */
	if (physmem < btop(24 << 20) && !(old_kmem_flags & KMF_STICKY))
		kmem_flags = 0;

	/*
	 * Don't do firewalled allocations if the heap is less than 1TB
	 * (i.e. on a 32-bit kernel)
	 * The resulting VM_NEXTFIT allocations would create too much
	 * fragmentation in a small heap.
	 */
#if defined(_LP64)
	maxverify = minfirewall = PAGESIZE / 2;
#else
	maxverify = minfirewall = ULONG_MAX;
#endif

	/* LINTED */
	ASSERT(sizeof (kmem_cpu_cache_t) == KMEM_CPU_CACHE_SIZE);

	list_create(&kmem_caches, sizeof (kmem_cache_t),
	    offsetof(kmem_cache_t, cache_link));

	kmem_metadata_arena = vmem_create("kmem_metadata", NULL, 0, PAGESIZE,
	    vmem_alloc, vmem_free, heap_arena, 8 * PAGESIZE,
	    VM_SLEEP | VMC_NO_QCACHE);

	kmem_msb_arena = vmem_create("kmem_msb", NULL, 0,
	    PAGESIZE, segkmem_alloc, segkmem_free, kmem_metadata_arena, 0,
	    VM_SLEEP);

	kmem_cache_arena = vmem_create("kmem_cache", NULL, 0, KMEM_ALIGN,
	    segkmem_alloc, segkmem_free, kmem_metadata_arena, 0, VM_SLEEP);

	kmem_hash_arena = vmem_create("kmem_hash", NULL, 0, KMEM_ALIGN,
	    segkmem_alloc, segkmem_free, kmem_metadata_arena, 0, VM_SLEEP);

	kmem_log_arena = vmem_create("kmem_log", NULL, 0, KMEM_ALIGN,
	    segkmem_alloc, segkmem_free, heap_arena, 0, VM_SLEEP);

	kmem_firewall_va_arena = vmem_create("kmem_firewall_va",
	    NULL, 0, PAGESIZE,
	    kmem_firewall_va_alloc, kmem_firewall_va_free, heap_arena,
	    0, VM_SLEEP);

	kmem_firewall_arena = vmem_create("kmem_firewall", NULL, 0, PAGESIZE,
	    segkmem_alloc, segkmem_free, kmem_firewall_va_arena, 0, VM_SLEEP);

	/* temporary oversize arena for mod_read_system_file */
	kmem_oversize_arena = vmem_create("kmem_oversize", NULL, 0, PAGESIZE,
	    segkmem_alloc, segkmem_free, heap_arena, 0, VM_SLEEP);

	kmem_reap_interval = 15 * hz;

	/*
	 * Read /etc/system.  This is a chicken-and-egg problem because
	 * kmem_flags may be set in /etc/system, but mod_read_system_file()
	 * needs to use the allocator.  The simplest solution is to create
	 * all the standard kmem caches, read /etc/system, destroy all the
	 * caches we just created, and then create them all again in light
	 * of the (possibly) new kmem_flags and other kmem tunables.
	 */
	kmem_cache_init(1, 0);

	mod_read_system_file(boothowto & RB_ASKNAME);

	while ((cp = list_tail(&kmem_caches)) != NULL)
		kmem_cache_destroy(cp);

	vmem_destroy(kmem_oversize_arena);

	if (old_kmem_flags & KMF_STICKY)
		kmem_flags = old_kmem_flags;

	if (!(kmem_flags & KMF_AUDIT))
		vmem_seg_size = offsetof(vmem_seg_t, vs_thread);

	if (kmem_maxverify == 0)
		kmem_maxverify = maxverify;

	if (kmem_minfirewall == 0)
		kmem_minfirewall = minfirewall;

	/*
	 * give segkmem a chance to figure out if we are using large pages
	 * for the kernel heap
	 */
	use_large_pages = segkmem_lpsetup();

	/*
	 * To protect against corruption, we keep the actual number of callers
	 * KMF_LITE records seperate from the tunable.  We arbitrarily clamp
	 * to 16, since the overhead for small buffers quickly gets out of
	 * hand.
	 *
	 * The real limit would depend on the needs of the largest KMC_NOHASH
	 * cache.
	 */
	kmem_lite_count = MIN(MAX(0, kmem_lite_pcs), 16);
	kmem_lite_pcs = kmem_lite_count;

	/*
	 * Normally, we firewall oversized allocations when possible, but
	 * if we are using large pages for kernel memory, and we don't have
	 * any non-LITE debugging flags set, we want to allocate oversized
	 * buffers from large pages, and so skip the firewalling.
	 */
	if (use_large_pages &&
	    ((kmem_flags & KMF_LITE) || !(kmem_flags & KMF_DEBUG))) {
		kmem_oversize_arena = vmem_xcreate("kmem_oversize", NULL, 0,
		    PAGESIZE, segkmem_alloc_lp, segkmem_free_lp, heap_arena,
		    0, VM_SLEEP);
	} else {
		kmem_oversize_arena = vmem_create("kmem_oversize",
		    NULL, 0, PAGESIZE,
		    segkmem_alloc, segkmem_free, kmem_minfirewall < ULONG_MAX?
		    kmem_firewall_va_arena : heap_arena, 0, VM_SLEEP);
	}

	kmem_cache_init(2, use_large_pages);

	if (kmem_flags & (KMF_AUDIT | KMF_RANDOMIZE)) {
		if (kmem_transaction_log_size == 0)
			kmem_transaction_log_size = kmem_maxavail() / 50;
		kmem_transaction_log = kmem_log_init(kmem_transaction_log_size);
	}

	if (kmem_flags & (KMF_CONTENTS | KMF_RANDOMIZE)) {
		if (kmem_content_log_size == 0)
			kmem_content_log_size = kmem_maxavail() / 50;
		kmem_content_log = kmem_log_init(kmem_content_log_size);
	}

	kmem_failure_log = kmem_log_init(kmem_failure_log_size);

	kmem_slab_log = kmem_log_init(kmem_slab_log_size);

	/*
	 * Initialize STREAMS message caches so allocb() is available.
	 * This allows us to initialize the logging framework (cmn_err(9F),
	 * strlog(9F), etc) so we can start recording messages.
	 */
	streams_msg_init();

	/*
	 * Initialize the ZSD framework in Zones so modules loaded henceforth
	 * can register their callbacks.
	 */
	zone_zsd_init();

	log_init();
	taskq_init();

	/*
	 * Warn about invalid or dangerous values of kmem_flags.
	 * Always warn about unsupported values.
	 */
	if (((kmem_flags & ~(KMF_AUDIT | KMF_DEADBEEF | KMF_REDZONE |
	    KMF_CONTENTS | KMF_LITE)) != 0) ||
	    ((kmem_flags & KMF_LITE) && kmem_flags != KMF_LITE))
		cmn_err(CE_WARN, "kmem_flags set to unsupported value 0x%x. "
		    "See the Solaris Tunable Parameters Reference Manual.",
		    kmem_flags);

#ifdef DEBUG
	if ((kmem_flags & KMF_DEBUG) == 0)
		cmn_err(CE_NOTE, "kmem debugging disabled.");
#else
	/*
	 * For non-debug kernels, the only "normal" flags are 0, KMF_LITE,
	 * KMF_REDZONE, and KMF_CONTENTS (the last because it is only enabled
	 * if KMF_AUDIT is set). We should warn the user about the performance
	 * penalty of KMF_AUDIT or KMF_DEADBEEF if they are set and KMF_LITE
	 * isn't set (since that disables AUDIT).
	 */
	if (!(kmem_flags & KMF_LITE) &&
	    (kmem_flags & (KMF_AUDIT | KMF_DEADBEEF)) != 0)
		cmn_err(CE_WARN, "High-overhead kmem debugging features "
		    "enabled (kmem_flags = 0x%x).  Performance degradation "
		    "and large memory overhead possible. See the Solaris "
		    "Tunable Parameters Reference Manual.", kmem_flags);
#endif /* not DEBUG */

	kmem_cache_applyall(kmem_cache_magazine_enable, NULL, TQ_SLEEP);

	kmem_ready = 1;

	/*
	 * Initialize the platform-specific aligned/DMA memory allocator.
	 */
	ka_init();

	/*
	 * Initialize 32-bit ID cache.
	 */
	id32_init();

	/*
	 * Initialize the networking stack so modules loaded can
	 * register their callbacks.
	 */
	netstack_init();
}

static void
kmem_move_init(void)
{
	kmem_defrag_cache = kmem_cache_create("kmem_defrag_cache",
	    sizeof (kmem_defrag_t), 0, NULL, NULL, NULL, NULL,
	    kmem_msb_arena, KMC_NOHASH);
	kmem_move_cache = kmem_cache_create("kmem_move_cache",
	    sizeof (kmem_move_t), 0, NULL, NULL, NULL, NULL,
	    kmem_msb_arena, KMC_NOHASH);

	/*
	 * kmem guarantees that move callbacks are sequential and that even
	 * across multiple caches no two moves ever execute simultaneously.
	 * Move callbacks are processed on a separate taskq so that client code
	 * does not interfere with internal maintenance tasks.
	 */
	kmem_move_taskq = taskq_create_instance("kmem_move_taskq", 0, 1,
	    minclsyspri, 100, INT_MAX, TASKQ_PREPOPULATE);
}

void
kmem_thread_init(void)
{
	kmem_move_init();
	kmem_taskq = taskq_create_instance("kmem_taskq", 0, 1, minclsyspri,
	    300, INT_MAX, TASKQ_PREPOPULATE);
}

void
kmem_mp_init(void)
{
	mutex_enter(&cpu_lock);
	register_cpu_setup_func(kmem_cpu_setup, NULL);
	mutex_exit(&cpu_lock);

	kmem_update_timeout(NULL);
}

/*
 * Return the slab of the allocated buffer, or NULL if the buffer is not
 * allocated. This function may be called with a known slab address to determine
 * whether or not the buffer is allocated, or with a NULL slab address to obtain
 * an allocated buffer's slab.
 */
static kmem_slab_t *
kmem_slab_allocated(kmem_cache_t *cp, kmem_slab_t *sp, void *buf)
{
	kmem_bufctl_t *bcp, *bufbcp;

	ASSERT(MUTEX_HELD(&cp->cache_lock));
	ASSERT(sp == NULL || KMEM_SLAB_MEMBER(sp, buf));

	if (cp->cache_flags & KMF_HASH) {
		for (bcp = *KMEM_HASH(cp, buf);
		    (bcp != NULL) && (bcp->bc_addr != buf);
		    bcp = bcp->bc_next) {
			continue;
		}
		ASSERT(sp != NULL && bcp != NULL ? sp == bcp->bc_slab : 1);
		return (bcp == NULL ? NULL : bcp->bc_slab);
	}

	if (sp == NULL) {
		sp = KMEM_SLAB(cp, buf);
	}
	bufbcp = KMEM_BUFCTL(cp, buf);
	for (bcp = sp->slab_head;
	    (bcp != NULL) && (bcp != bufbcp);
	    bcp = bcp->bc_next) {
		continue;
	}
	return (bcp == NULL ? sp : NULL);
}

static boolean_t
kmem_slab_is_reclaimable(kmem_cache_t *cp, kmem_slab_t *sp, int flags)
{
	long refcnt;

	ASSERT(cp->cache_defrag != NULL);

	/* If we're desperate, we don't care if the client said NO. */
	refcnt = sp->slab_refcnt;
	if (flags & KMM_DESPERATE) {
		return (refcnt < sp->slab_chunks); /* any partial */
	}

	if (sp->slab_flags & KMEM_SLAB_NOMOVE) {
		return (B_FALSE);
	}

	if (kmem_move_any_partial) {
		return (refcnt < sp->slab_chunks);
	}

	if ((refcnt == 1) && (refcnt < sp->slab_chunks)) {
		return (B_TRUE);
	}

	/*
	 * The reclaim threshold is adjusted at each kmem_cache_scan() so that
	 * slabs with a progressively higher percentage of used buffers can be
	 * reclaimed until the cache as a whole is no longer fragmented.
	 *
	 *	sp->slab_refcnt   kmd_reclaim_numer
	 *	--------------- < ------------------
	 *	sp->slab_chunks   KMEM_VOID_FRACTION
	 */
	return ((refcnt * KMEM_VOID_FRACTION) <
	    (sp->slab_chunks * cp->cache_defrag->kmd_reclaim_numer));
}

static void *
kmem_hunt_mag(kmem_cache_t *cp, kmem_magazine_t *m, int n, void *buf,
    void *tbuf)
{
	int i;		/* magazine round index */

	for (i = 0; i < n; i++) {
		if (buf == m->mag_round[i]) {
			if (cp->cache_flags & KMF_BUFTAG) {
				(void) kmem_cache_free_debug(cp, tbuf,
				    caller());
			}
			m->mag_round[i] = tbuf;
			return (buf);
		}
	}

	return (NULL);
}

/*
 * Hunt the magazine layer for the given buffer. If found, the buffer is
 * removed from the magazine layer and returned, otherwise NULL is returned.
 * The state of the returned buffer is freed and constructed.
 */
static void *
kmem_hunt_mags(kmem_cache_t *cp, void *buf)
{
	kmem_cpu_cache_t *ccp;
	kmem_magazine_t	*m;
	int cpu_seqid;
	int n;		/* magazine rounds */
	void *tbuf;	/* temporary swap buffer */

	ASSERT(MUTEX_NOT_HELD(&cp->cache_lock));

	/*
	 * Allocated a buffer to swap with the one we hope to pull out of a
	 * magazine when found.
	 */
	tbuf = kmem_cache_alloc(cp, KM_NOSLEEP);
	if (tbuf == NULL) {
		KMEM_STAT_ADD(kmem_move_stats.kms_hunt_alloc_fail);
		return (NULL);
	}
	if (tbuf == buf) {
		KMEM_STAT_ADD(kmem_move_stats.kms_hunt_lucky);
		if (cp->cache_flags & KMF_BUFTAG) {
			(void) kmem_cache_free_debug(cp, buf, caller());
		}
		return (buf);
	}

	/* Hunt the depot. */
	mutex_enter(&cp->cache_depot_lock);
	n = cp->cache_magtype->mt_magsize;
	for (m = cp->cache_full.ml_list; m != NULL; m = m->mag_next) {
		if (kmem_hunt_mag(cp, m, n, buf, tbuf) != NULL) {
			mutex_exit(&cp->cache_depot_lock);
			return (buf);
		}
	}
	mutex_exit(&cp->cache_depot_lock);

	/* Hunt the per-CPU magazines. */
	for (cpu_seqid = 0; cpu_seqid < max_ncpus; cpu_seqid++) {
		ccp = &cp->cache_cpu[cpu_seqid];

		mutex_enter(&ccp->cc_lock);
		m = ccp->cc_loaded;
		n = ccp->cc_rounds;
		if (kmem_hunt_mag(cp, m, n, buf, tbuf) != NULL) {
			mutex_exit(&ccp->cc_lock);
			return (buf);
		}
		m = ccp->cc_ploaded;
		n = ccp->cc_prounds;
		if (kmem_hunt_mag(cp, m, n, buf, tbuf) != NULL) {
			mutex_exit(&ccp->cc_lock);
			return (buf);
		}
		mutex_exit(&ccp->cc_lock);
	}

	kmem_cache_free(cp, tbuf);
	return (NULL);
}

/*
 * May be called from the kmem_move_taskq, from kmem_cache_move_notify_task(),
 * or when the buffer is freed.
 */
static void
kmem_slab_move_yes(kmem_cache_t *cp, kmem_slab_t *sp, void *from_buf)
{
	ASSERT(MUTEX_HELD(&cp->cache_lock));
	ASSERT(KMEM_SLAB_MEMBER(sp, from_buf));

	if (!KMEM_SLAB_IS_PARTIAL(sp)) {
		return;
	}

	if (sp->slab_flags & KMEM_SLAB_NOMOVE) {
		if (KMEM_SLAB_OFFSET(sp, from_buf) == sp->slab_stuck_offset) {
			avl_remove(&cp->cache_partial_slabs, sp);
			sp->slab_flags &= ~KMEM_SLAB_NOMOVE;
			sp->slab_stuck_offset = (uint32_t)-1;
			avl_add(&cp->cache_partial_slabs, sp);
		}
	} else {
		sp->slab_later_count = 0;
		sp->slab_stuck_offset = (uint32_t)-1;
	}
}

static void
kmem_slab_move_no(kmem_cache_t *cp, kmem_slab_t *sp, void *from_buf)
{
	ASSERT(taskq_member(kmem_move_taskq, curthread));
	ASSERT(MUTEX_HELD(&cp->cache_lock));
	ASSERT(KMEM_SLAB_MEMBER(sp, from_buf));

	if (!KMEM_SLAB_IS_PARTIAL(sp)) {
		return;
	}

	avl_remove(&cp->cache_partial_slabs, sp);
	sp->slab_later_count = 0;
	sp->slab_flags |= KMEM_SLAB_NOMOVE;
	sp->slab_stuck_offset = KMEM_SLAB_OFFSET(sp, from_buf);
	avl_add(&cp->cache_partial_slabs, sp);
}

static void kmem_move_end(kmem_cache_t *, kmem_move_t *);

/*
 * The move callback takes two buffer addresses, the buffer to be moved, and a
 * newly allocated and constructed buffer selected by kmem as the destination.
 * It also takes the size of the buffer and an optional user argument specified
 * at cache creation time. kmem guarantees that the buffer to be moved has not
 * been unmapped by the virtual memory subsystem. Beyond that, it cannot
 * guarantee the present whereabouts of the buffer to be moved, so it is up to
 * the client to safely determine whether or not it is still using the buffer.
 * The client must not free either of the buffers passed to the move callback,
 * since kmem wants to free them directly to the slab layer. The client response
 * tells kmem which of the two buffers to free:
 *
 * YES		kmem frees the old buffer (the move was successful)
 * NO		kmem frees the new buffer, marks the slab of the old buffer
 *              non-reclaimable to avoid bothering the client again
 * LATER	kmem frees the new buffer, increments slab_later_count
 * DONT_KNOW	kmem frees the new buffer, searches mags for the old buffer
 * DONT_NEED	kmem frees both the old buffer and the new buffer
 *
 * The pending callback argument now being processed contains both of the
 * buffers (old and new) passed to the move callback function, the slab of the
 * old buffer, and flags related to the move request, such as whether or not the
 * system was desperate for memory.
 */
static void
kmem_move_buffer(kmem_move_t *callback)
{
	kmem_cbrc_t response;
	kmem_slab_t *sp = callback->kmm_from_slab;
	kmem_cache_t *cp = sp->slab_cache;
	boolean_t free_on_slab;

	ASSERT(taskq_member(kmem_move_taskq, curthread));
	ASSERT(MUTEX_NOT_HELD(&cp->cache_lock));
	ASSERT(KMEM_SLAB_MEMBER(sp, callback->kmm_from_buf));

	/*
	 * The number of allocated buffers on the slab may have changed since we
	 * last checked the slab's reclaimability (when the pending move was
	 * enqueued), or the client may have responded NO when asked to move
	 * another buffer on the same slab.
	 */
	if (!kmem_slab_is_reclaimable(cp, sp, callback->kmm_flags)) {
		KMEM_STAT_ADD(kmem_move_stats.kms_no_longer_reclaimable);
		KMEM_STAT_COND_ADD((callback->kmm_flags & KMM_NOTIFY),
		    kmem_move_stats.kms_notify_no_longer_reclaimable);
		kmem_slab_free(cp, callback->kmm_to_buf);
		kmem_move_end(cp, callback);
		return;
	}

	/*
	 * Hunting magazines is expensive, so we'll wait to do that until the
	 * client responds KMEM_CBRC_DONT_KNOW. However, checking the slab layer
	 * is cheap, so we might as well do that here in case we can avoid
	 * bothering the client.
	 */
	mutex_enter(&cp->cache_lock);
	free_on_slab = (kmem_slab_allocated(cp, sp,
	    callback->kmm_from_buf) == NULL);
	mutex_exit(&cp->cache_lock);

	if (free_on_slab) {
		KMEM_STAT_ADD(kmem_move_stats.kms_hunt_found_slab);
		kmem_slab_free(cp, callback->kmm_to_buf);
		kmem_move_end(cp, callback);
		return;
	}

	if (cp->cache_flags & KMF_BUFTAG) {
		/*
		 * Make kmem_cache_alloc_debug() apply the constructor for us.
		 */
		if (kmem_cache_alloc_debug(cp, callback->kmm_to_buf,
		    KM_NOSLEEP, 1, caller()) != 0) {
			KMEM_STAT_ADD(kmem_move_stats.kms_alloc_fail);
			kmem_move_end(cp, callback);
			return;
		}
	} else if (cp->cache_constructor != NULL &&
	    cp->cache_constructor(callback->kmm_to_buf, cp->cache_private,
	    KM_NOSLEEP) != 0) {
		atomic_add_64(&cp->cache_alloc_fail, 1);
		KMEM_STAT_ADD(kmem_move_stats.kms_constructor_fail);
		kmem_slab_free(cp, callback->kmm_to_buf);
		kmem_move_end(cp, callback);
		return;
	}

	KMEM_STAT_ADD(kmem_move_stats.kms_callbacks);
	KMEM_STAT_COND_ADD((callback->kmm_flags & KMM_NOTIFY),
	    kmem_move_stats.kms_notify_callbacks);
	cp->cache_defrag->kmd_callbacks++;
	cp->cache_defrag->kmd_thread = curthread;
	cp->cache_defrag->kmd_from_buf = callback->kmm_from_buf;
	cp->cache_defrag->kmd_to_buf = callback->kmm_to_buf;
	DTRACE_PROBE2(kmem__move__start, kmem_cache_t *, cp, kmem_move_t *,
	    callback);

	response = cp->cache_move(callback->kmm_from_buf,
	    callback->kmm_to_buf, cp->cache_bufsize, cp->cache_private);

	DTRACE_PROBE3(kmem__move__end, kmem_cache_t *, cp, kmem_move_t *,
	    callback, kmem_cbrc_t, response);
	cp->cache_defrag->kmd_thread = NULL;
	cp->cache_defrag->kmd_from_buf = NULL;
	cp->cache_defrag->kmd_to_buf = NULL;

	if (response == KMEM_CBRC_YES) {
		KMEM_STAT_ADD(kmem_move_stats.kms_yes);
		cp->cache_defrag->kmd_yes++;
		kmem_slab_free_constructed(cp, callback->kmm_from_buf, B_FALSE);
		mutex_enter(&cp->cache_lock);
		kmem_slab_move_yes(cp, sp, callback->kmm_from_buf);
		mutex_exit(&cp->cache_lock);
		kmem_move_end(cp, callback);
		return;
	}

	switch (response) {
	case KMEM_CBRC_NO:
		KMEM_STAT_ADD(kmem_move_stats.kms_no);
		cp->cache_defrag->kmd_no++;
		mutex_enter(&cp->cache_lock);
		kmem_slab_move_no(cp, sp, callback->kmm_from_buf);
		mutex_exit(&cp->cache_lock);
		break;
	case KMEM_CBRC_LATER:
		KMEM_STAT_ADD(kmem_move_stats.kms_later);
		cp->cache_defrag->kmd_later++;
		mutex_enter(&cp->cache_lock);
		if (!KMEM_SLAB_IS_PARTIAL(sp)) {
			mutex_exit(&cp->cache_lock);
			break;
		}

		if (++sp->slab_later_count >= KMEM_DISBELIEF) {
			KMEM_STAT_ADD(kmem_move_stats.kms_disbelief);
			kmem_slab_move_no(cp, sp, callback->kmm_from_buf);
		} else if (!(sp->slab_flags & KMEM_SLAB_NOMOVE)) {
			sp->slab_stuck_offset = KMEM_SLAB_OFFSET(sp,
			    callback->kmm_from_buf);
		}
		mutex_exit(&cp->cache_lock);
		break;
	case KMEM_CBRC_DONT_NEED:
		KMEM_STAT_ADD(kmem_move_stats.kms_dont_need);
		cp->cache_defrag->kmd_dont_need++;
		kmem_slab_free_constructed(cp, callback->kmm_from_buf, B_FALSE);
		mutex_enter(&cp->cache_lock);
		kmem_slab_move_yes(cp, sp, callback->kmm_from_buf);
		mutex_exit(&cp->cache_lock);
		break;
	case KMEM_CBRC_DONT_KNOW:
		KMEM_STAT_ADD(kmem_move_stats.kms_dont_know);
		cp->cache_defrag->kmd_dont_know++;
		if (kmem_hunt_mags(cp, callback->kmm_from_buf) != NULL) {
			KMEM_STAT_ADD(kmem_move_stats.kms_hunt_found_mag);
			cp->cache_defrag->kmd_hunt_found++;
			kmem_slab_free_constructed(cp, callback->kmm_from_buf,
			    B_TRUE);
			mutex_enter(&cp->cache_lock);
			kmem_slab_move_yes(cp, sp, callback->kmm_from_buf);
			mutex_exit(&cp->cache_lock);
		}
		break;
	default:
		panic("'%s' (%p) unexpected move callback response %d\n",
		    cp->cache_name, (void *)cp, response);
	}

	kmem_slab_free_constructed(cp, callback->kmm_to_buf, B_FALSE);
	kmem_move_end(cp, callback);
}

/* Return B_FALSE if there is insufficient memory for the move request. */
static boolean_t
kmem_move_begin(kmem_cache_t *cp, kmem_slab_t *sp, void *buf, int flags)
{
	void *to_buf;
	avl_index_t index;
	kmem_move_t *callback, *pending;

	ASSERT(taskq_member(kmem_taskq, curthread));
	ASSERT(MUTEX_NOT_HELD(&cp->cache_lock));
	ASSERT(sp->slab_flags & KMEM_SLAB_MOVE_PENDING);

	callback = kmem_cache_alloc(kmem_move_cache, KM_NOSLEEP);
	if (callback == NULL) {
		KMEM_STAT_ADD(kmem_move_stats.kms_callback_alloc_fail);
		return (B_FALSE);
	}

	callback->kmm_from_slab = sp;
	callback->kmm_from_buf = buf;
	callback->kmm_flags = flags;

	mutex_enter(&cp->cache_lock);

	if (avl_numnodes(&cp->cache_partial_slabs) <= 1) {
		mutex_exit(&cp->cache_lock);
		kmem_cache_free(kmem_move_cache, callback);
		return (B_TRUE); /* there is no need for the move request */
	}

	pending = avl_find(&cp->cache_defrag->kmd_moves_pending, buf, &index);
	if (pending != NULL) {
		/*
		 * If the move is already pending and we're desperate now,
		 * update the move flags.
		 */
		if (flags & KMM_DESPERATE) {
			pending->kmm_flags |= KMM_DESPERATE;
		}
		mutex_exit(&cp->cache_lock);
		KMEM_STAT_ADD(kmem_move_stats.kms_already_pending);
		kmem_cache_free(kmem_move_cache, callback);
		return (B_TRUE);
	}

	to_buf = kmem_slab_alloc_impl(cp, avl_first(&cp->cache_partial_slabs));
	callback->kmm_to_buf = to_buf;
	avl_insert(&cp->cache_defrag->kmd_moves_pending, callback, index);

	mutex_exit(&cp->cache_lock);

	if (!taskq_dispatch(kmem_move_taskq, (task_func_t *)kmem_move_buffer,
	    callback, TQ_NOSLEEP)) {
		KMEM_STAT_ADD(kmem_move_stats.kms_callback_taskq_fail);
		mutex_enter(&cp->cache_lock);
		avl_remove(&cp->cache_defrag->kmd_moves_pending, callback);
		mutex_exit(&cp->cache_lock);
		kmem_slab_free(cp, to_buf);
		kmem_cache_free(kmem_move_cache, callback);
		return (B_FALSE);
	}

	return (B_TRUE);
}

static void
kmem_move_end(kmem_cache_t *cp, kmem_move_t *callback)
{
	avl_index_t index;

	ASSERT(cp->cache_defrag != NULL);
	ASSERT(taskq_member(kmem_move_taskq, curthread));
	ASSERT(MUTEX_NOT_HELD(&cp->cache_lock));

	mutex_enter(&cp->cache_lock);
	VERIFY(avl_find(&cp->cache_defrag->kmd_moves_pending,
	    callback->kmm_from_buf, &index) != NULL);
	avl_remove(&cp->cache_defrag->kmd_moves_pending, callback);
	if (avl_is_empty(&cp->cache_defrag->kmd_moves_pending)) {
		list_t *deadlist = &cp->cache_defrag->kmd_deadlist;
		kmem_slab_t *sp;

		/*
		 * The last pending move completed. Release all slabs from the
		 * front of the dead list except for any slab at the tail that
		 * needs to be released from the context of kmem_move_buffers().
		 * kmem deferred unmapping the buffers on these slabs in order
		 * to guarantee that buffers passed to the move callback have
		 * been touched only by kmem or by the client itself.
		 */
		while ((sp = list_remove_head(deadlist)) != NULL) {
			if (sp->slab_flags & KMEM_SLAB_MOVE_PENDING) {
				list_insert_tail(deadlist, sp);
				break;
			}
			cp->cache_defrag->kmd_deadcount--;
			cp->cache_slab_destroy++;
			mutex_exit(&cp->cache_lock);
			kmem_slab_destroy(cp, sp);
			KMEM_STAT_ADD(kmem_move_stats.kms_dead_slabs_freed);
			mutex_enter(&cp->cache_lock);
		}
	}
	mutex_exit(&cp->cache_lock);
	kmem_cache_free(kmem_move_cache, callback);
}

/*
 * Move buffers from least used slabs first by scanning backwards from the end
 * of the partial slab list. Scan at most max_scan candidate slabs and move
 * buffers from at most max_slabs slabs (0 for all partial slabs in both cases).
 * If desperate to reclaim memory, move buffers from any partial slab, otherwise
 * skip slabs with a ratio of allocated buffers at or above the current
 * threshold. Return the number of unskipped slabs (at most max_slabs, -1 if the
 * scan is aborted) so that the caller can adjust the reclaimability threshold
 * depending on how many reclaimable slabs it finds.
 *
 * kmem_move_buffers() drops and reacquires cache_lock every time it issues a
 * move request, since it is not valid for kmem_move_begin() to call
 * kmem_cache_alloc() or taskq_dispatch() with cache_lock held.
 */
static int
kmem_move_buffers(kmem_cache_t *cp, size_t max_scan, size_t max_slabs,
    int flags)
{
	kmem_slab_t *sp;
	void *buf;
	int i, j; /* slab index, buffer index */
	int s; /* reclaimable slabs */
	int b; /* allocated (movable) buffers on reclaimable slab */
	boolean_t success;
	int refcnt;
	int nomove;

	ASSERT(taskq_member(kmem_taskq, curthread));
	ASSERT(MUTEX_HELD(&cp->cache_lock));
	ASSERT(kmem_move_cache != NULL);
	ASSERT(cp->cache_move != NULL && cp->cache_defrag != NULL);
	ASSERT(avl_numnodes(&cp->cache_partial_slabs) > 1);

	if (kmem_move_blocked) {
		return (0);
	}

	if (kmem_move_fulltilt) {
		max_slabs = 0;
		flags |= KMM_DESPERATE;
	}

	if (max_scan == 0 || (flags & KMM_DESPERATE)) {
		/*
		 * Scan as many slabs as needed to find the desired number of
		 * candidate slabs.
		 */
		max_scan = (size_t)-1;
	}

	if (max_slabs == 0 || (flags & KMM_DESPERATE)) {
		/* Find as many candidate slabs as possible. */
		max_slabs = (size_t)-1;
	}

	sp = avl_last(&cp->cache_partial_slabs);
	ASSERT(sp != NULL && KMEM_SLAB_IS_PARTIAL(sp));
	for (i = 0, s = 0; (i < max_scan) && (s < max_slabs) &&
	    (sp != avl_first(&cp->cache_partial_slabs));
	    sp = AVL_PREV(&cp->cache_partial_slabs, sp), i++) {

		if (!kmem_slab_is_reclaimable(cp, sp, flags)) {
			continue;
		}
		s++;

		/* Look for allocated buffers to move. */
		for (j = 0, b = 0, buf = sp->slab_base;
		    (j < sp->slab_chunks) && (b < sp->slab_refcnt);
		    buf = (((char *)buf) + cp->cache_chunksize), j++) {

			if (kmem_slab_allocated(cp, sp, buf) == NULL) {
				continue;
			}

			b++;

			/*
			 * Prevent the slab from being destroyed while we drop
			 * cache_lock and while the pending move is not yet
			 * registered. Flag the pending move while
			 * kmd_moves_pending may still be empty, since we can't
			 * yet rely on a non-zero pending move count to prevent
			 * the slab from being destroyed.
			 */
			ASSERT(!(sp->slab_flags & KMEM_SLAB_MOVE_PENDING));
			sp->slab_flags |= KMEM_SLAB_MOVE_PENDING;
			/*
			 * Recheck refcnt and nomove after reacquiring the lock,
			 * since these control the order of partial slabs, and
			 * we want to know if we can pick up the scan where we
			 * left off.
			 */
			refcnt = sp->slab_refcnt;
			nomove = (sp->slab_flags & KMEM_SLAB_NOMOVE);
			mutex_exit(&cp->cache_lock);

			success = kmem_move_begin(cp, sp, buf, flags);

			/*
			 * Now, before the lock is reacquired, kmem could
			 * process all pending move requests and purge the
			 * deadlist, so that upon reacquiring the lock, sp has
			 * been remapped. Therefore, the KMEM_SLAB_MOVE_PENDING
			 * flag causes the slab to be put at the end of the
			 * deadlist and prevents it from being purged, since we
			 * plan to destroy it here after reacquiring the lock.
			 */
			mutex_enter(&cp->cache_lock);
			ASSERT(sp->slab_flags & KMEM_SLAB_MOVE_PENDING);
			sp->slab_flags &= ~KMEM_SLAB_MOVE_PENDING;

			/*
			 * Destroy the slab now if it was completely freed while
			 * we dropped cache_lock.
			 */
			if (sp->slab_refcnt == 0) {
				list_t *deadlist =
				    &cp->cache_defrag->kmd_deadlist;

				ASSERT(!list_is_empty(deadlist));
				ASSERT(list_link_active((list_node_t *)
				    &sp->slab_link));

				list_remove(deadlist, sp);
				cp->cache_defrag->kmd_deadcount--;
				cp->cache_slab_destroy++;
				mutex_exit(&cp->cache_lock);
				kmem_slab_destroy(cp, sp);
				KMEM_STAT_ADD(kmem_move_stats.
				    kms_dead_slabs_freed);
				KMEM_STAT_ADD(kmem_move_stats.
				    kms_endscan_slab_destroyed);
				mutex_enter(&cp->cache_lock);
				/*
				 * Since we can't pick up the scan where we left
				 * off, abort the scan and say nothing about the
				 * number of reclaimable slabs.
				 */
				return (-1);
			}

			if (!success) {
				/*
				 * Abort the scan if there is not enough memory
				 * for the request and say nothing about the
				 * number of reclaimable slabs.
				 */
				KMEM_STAT_ADD(
				    kmem_move_stats.kms_endscan_nomem);
				return (-1);
			}

			/*
			 * The slab may have been completely allocated while the
			 * lock was dropped.
			 */
			if (KMEM_SLAB_IS_ALL_USED(sp)) {
				KMEM_STAT_ADD(
				    kmem_move_stats.kms_endscan_slab_all_used);
				return (-1);
			}

			/*
			 * The slab's position changed while the lock was
			 * dropped, so we don't know where we are in the
			 * sequence any more.
			 */
			if (sp->slab_refcnt != refcnt) {
				KMEM_STAT_ADD(
				    kmem_move_stats.kms_endscan_refcnt_changed);
				return (-1);
			}
			if ((sp->slab_flags & KMEM_SLAB_NOMOVE) != nomove) {
				KMEM_STAT_ADD(
				    kmem_move_stats.kms_endscan_nomove_changed);
				return (-1);
			}

			/*
			 * Generating a move request allocates a destination
			 * buffer from the slab layer, bumping the first slab if
			 * it is completely allocated.
			 */
			ASSERT(!avl_is_empty(&cp->cache_partial_slabs));
			if (sp == avl_first(&cp->cache_partial_slabs)) {
				goto end_scan;
			}
		}
	}
end_scan:

	KMEM_STAT_COND_ADD(sp == avl_first(&cp->cache_partial_slabs),
	    kmem_move_stats.kms_endscan_freelist);

	return (s);
}

typedef struct kmem_move_notify_args {
	kmem_cache_t *kmna_cache;
	void *kmna_buf;
} kmem_move_notify_args_t;

static void
kmem_cache_move_notify_task(void *arg)
{
	kmem_move_notify_args_t *args = arg;
	kmem_cache_t *cp = args->kmna_cache;
	void *buf = args->kmna_buf;
	kmem_slab_t *sp;

	ASSERT(taskq_member(kmem_taskq, curthread));
	ASSERT(list_link_active(&cp->cache_link));

	kmem_free(args, sizeof (kmem_move_notify_args_t));
	mutex_enter(&cp->cache_lock);
	sp = kmem_slab_allocated(cp, NULL, buf);

	/* Ignore the notification if the buffer is no longer allocated. */
	if (sp == NULL) {
		mutex_exit(&cp->cache_lock);
		return;
	}

	/* Ignore the notification if there's no reason to move the buffer. */
	if (avl_numnodes(&cp->cache_partial_slabs) > 1) {
		/*
		 * So far the notification is not ignored. Ignore the
		 * notification if the slab is not marked by an earlier refusal
		 * to move a buffer.
		 */
		if (!(sp->slab_flags & KMEM_SLAB_NOMOVE) &&
		    (sp->slab_later_count == 0)) {
			mutex_exit(&cp->cache_lock);
			return;
		}

		kmem_slab_move_yes(cp, sp, buf);
		ASSERT(!(sp->slab_flags & KMEM_SLAB_MOVE_PENDING));
		sp->slab_flags |= KMEM_SLAB_MOVE_PENDING;
		mutex_exit(&cp->cache_lock);
		/* see kmem_move_buffers() about dropping the lock */
		(void) kmem_move_begin(cp, sp, buf, KMM_NOTIFY);
		mutex_enter(&cp->cache_lock);
		ASSERT(sp->slab_flags & KMEM_SLAB_MOVE_PENDING);
		sp->slab_flags &= ~KMEM_SLAB_MOVE_PENDING;
		if (sp->slab_refcnt == 0) {
			list_t *deadlist = &cp->cache_defrag->kmd_deadlist;

			ASSERT(!list_is_empty(deadlist));
			ASSERT(list_link_active((list_node_t *)
			    &sp->slab_link));

			list_remove(deadlist, sp);
			cp->cache_defrag->kmd_deadcount--;
			cp->cache_slab_destroy++;
			mutex_exit(&cp->cache_lock);
			kmem_slab_destroy(cp, sp);
			KMEM_STAT_ADD(kmem_move_stats.kms_dead_slabs_freed);
			return;
		}
	} else {
		kmem_slab_move_yes(cp, sp, buf);
	}
	mutex_exit(&cp->cache_lock);
}

void
kmem_cache_move_notify(kmem_cache_t *cp, void *buf)
{
	kmem_move_notify_args_t *args;

	KMEM_STAT_ADD(kmem_move_stats.kms_notify);
	args = kmem_alloc(sizeof (kmem_move_notify_args_t), KM_NOSLEEP);
	if (args != NULL) {
		args->kmna_cache = cp;
		args->kmna_buf = buf;
		if (!taskq_dispatch(kmem_taskq,
		    (task_func_t *)kmem_cache_move_notify_task, args,
		    TQ_NOSLEEP))
			kmem_free(args, sizeof (kmem_move_notify_args_t));
	}
}

static void
kmem_cache_defrag(kmem_cache_t *cp)
{
	size_t n;

	ASSERT(cp->cache_defrag != NULL);

	mutex_enter(&cp->cache_lock);
	n = avl_numnodes(&cp->cache_partial_slabs);
	if (n > 1) {
		/* kmem_move_buffers() drops and reacquires cache_lock */
		(void) kmem_move_buffers(cp, n, 0, KMM_DESPERATE);
		KMEM_STAT_ADD(kmem_move_stats.kms_defrags);
	}
	mutex_exit(&cp->cache_lock);
}

/* Is this cache above the fragmentation threshold? */
static boolean_t
kmem_cache_frag_threshold(kmem_cache_t *cp, uint64_t nfree)
{
	if (avl_numnodes(&cp->cache_partial_slabs) <= 1)
		return (B_FALSE);

	/*
	 *	nfree		kmem_frag_numer
	 * ------------------ > ---------------
	 * cp->cache_buftotal	kmem_frag_denom
	 */
	return ((nfree * kmem_frag_denom) >
	    (cp->cache_buftotal * kmem_frag_numer));
}

static boolean_t
kmem_cache_is_fragmented(kmem_cache_t *cp, boolean_t *doreap)
{
	boolean_t fragmented;
	uint64_t nfree;

	ASSERT(MUTEX_HELD(&cp->cache_lock));
	*doreap = B_FALSE;

	if (!kmem_move_fulltilt && ((cp->cache_complete_slab_count +
	    avl_numnodes(&cp->cache_partial_slabs)) < kmem_frag_minslabs))
		return (B_FALSE);

	nfree = cp->cache_bufslab;
	fragmented = kmem_cache_frag_threshold(cp, nfree);
	/*
	 * Free buffers in the magazine layer appear allocated from the point of
	 * view of the slab layer. We want to know if the slab layer would
	 * appear fragmented if we included free buffers from magazines that
	 * have fallen out of the working set.
	 */
	if (!fragmented) {
		long reap;

		mutex_enter(&cp->cache_depot_lock);
		reap = MIN(cp->cache_full.ml_reaplimit, cp->cache_full.ml_min);
		reap = MIN(reap, cp->cache_full.ml_total);
		mutex_exit(&cp->cache_depot_lock);

		nfree += ((uint64_t)reap * cp->cache_magtype->mt_magsize);
		if (kmem_cache_frag_threshold(cp, nfree)) {
			*doreap = B_TRUE;
		}
	}

	return (fragmented);
}

/* Called periodically from kmem_taskq */
static void
kmem_cache_scan(kmem_cache_t *cp)
{
	boolean_t reap = B_FALSE;

	ASSERT(taskq_member(kmem_taskq, curthread));
	ASSERT(cp->cache_defrag != NULL);

	mutex_enter(&cp->cache_lock);

	if (kmem_cache_is_fragmented(cp, &reap)) {
		kmem_defrag_t *kmd = cp->cache_defrag;
		size_t slabs_found;

		/*
		 * Consolidate reclaimable slabs from the end of the partial
		 * slab list (scan at most kmem_reclaim_scan_range slabs to find
		 * reclaimable slabs). Keep track of how many candidate slabs we
		 * looked for and how many we actually found so we can adjust
		 * the definition of a candidate slab if we're having trouble
		 * finding them.
		 *
		 * kmem_move_buffers() drops and reacquires cache_lock.
		 */
		slabs_found = kmem_move_buffers(cp, kmem_reclaim_scan_range,
		    kmem_reclaim_max_slabs, 0);
		if (slabs_found >= 0) {
			kmd->kmd_slabs_sought += kmem_reclaim_max_slabs;
			kmd->kmd_slabs_found += slabs_found;
		}

		if (++kmd->kmd_scans >= kmem_reclaim_scan_range) {
			kmd->kmd_scans = 0;

			/*
			 * If we had difficulty finding candidate slabs in
			 * previous scans, adjust the threshold so that
			 * candidates are easier to find.
			 */
			if (kmd->kmd_slabs_found == kmd->kmd_slabs_sought) {
				kmem_adjust_reclaim_threshold(kmd, -1);
			} else if ((kmd->kmd_slabs_found * 2) <
			    kmd->kmd_slabs_sought) {
				kmem_adjust_reclaim_threshold(kmd, 1);
			}
			kmd->kmd_slabs_sought = 0;
			kmd->kmd_slabs_found = 0;
		}
	} else {
		kmem_reset_reclaim_threshold(cp->cache_defrag);
#ifdef	DEBUG
		if (avl_numnodes(&cp->cache_partial_slabs) > 1) {
			/*
			 * In a debug kernel we want the consolidator to
			 * run occasionally even when there is plenty of
			 * memory.
			 */
			uint32_t debug_rand;

			(void) random_get_bytes((uint8_t *)&debug_rand, 4);
			if (!kmem_move_noreap &&
			    ((debug_rand % kmem_mtb_reap) == 0)) {
				mutex_exit(&cp->cache_lock);
				kmem_cache_reap(cp);
				KMEM_STAT_ADD(kmem_move_stats.kms_debug_reaps);
				return;
			} else if ((debug_rand % kmem_mtb_move) == 0) {
				(void) kmem_move_buffers(cp,
				    kmem_reclaim_scan_range, 1, 0);
				KMEM_STAT_ADD(kmem_move_stats.
				    kms_debug_move_scans);
			}
		}
#endif	/* DEBUG */
	}

	mutex_exit(&cp->cache_lock);

	if (reap) {
		KMEM_STAT_ADD(kmem_move_stats.kms_scan_depot_ws_reaps);
		kmem_depot_ws_reap(cp);
	}
}