xref: /freebsd/sys/vm/uma_int.h (revision 6fc96493ac9d285d0e8913b3ad61eb35b1f28fe4)

/*
 * Copyright (c) 2002, Jeffrey Roberson <jeff@freebsd.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice unmodified, this list of conditions, and the following
 *    disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * $FreeBSD$
 *
 */

/*
 * This file includes definitions, structures, prototypes, and inlines that
 * should not be used outside of the actual implementation of UMA.
 */

/*
 * Here's a quick description of the relationship between the objects:
 *
 * Kegs contain lists of slabs which are stored in either the full bin, empty
 * bin, or partially allocated bin, to reduce fragmentation.  They also contain
 * the user supplied value for size, which is adjusted for alignment purposes
 * and rsize is the result of that.  The Keg also stores information for
 * managing a hash of page addresses that maps pages to uma_slab_t structures
 * for pages that don't have embedded uma_slab_t's.
 *
 * The uma_slab_t may be embedded in a UMA_SLAB_SIZE chunk of memory or it may
 * be allocated off the page from a special slab zone.  The free list within a
 * slab is managed with a linked list of indexes, which are 8 bit values.  If
 * UMA_SLAB_SIZE is defined to be too large I will have to switch to 16bit
 * values.  Currently on alpha you can get 250 or so 32 byte items and on x86
 * you can get 250 or so 16byte items.  For item sizes that would yield more
 * than 10% memory waste we potentially allocate a separate uma_slab_t if this
 * will improve the number of items per slab that will fit.
 *
 * Other potential space optimizations are storing the 8bit of linkage in space
 * wasted between items due to alignment problems.  This may yield a much better
 * memory footprint for certain sizes of objects.  Another alternative is to
 * increase the UMA_SLAB_SIZE, or allow for dynamic slab sizes.  I prefer
 * dynamic slab sizes because we could stick with 8 bit indexes and only use
 * large slab sizes for zones with a lot of waste per slab.  This may create
 * ineffeciencies in the vm subsystem due to fragmentation in the address space.
 *
 * The only really gross cases, with regards to memory waste, are for those
 * items that are just over half the page size.   You can get nearly 50% waste,
 * so you fall back to the memory footprint of the power of two allocator. I
 * have looked at memory allocation sizes on many of the machines available to
 * me, and there does not seem to be an abundance of allocations at this range
 * so at this time it may not make sense to optimize for it.  This can, of
 * course, be solved with dynamic slab sizes.
 *
 * Kegs may serve multiple Zones but by far most of the time they only serve
 * one.  When a Zone is created, a Keg is allocated and setup for it.  While
 * the backing Keg stores slabs, the Zone caches Buckets of items allocated
 * from the slabs.  Each Zone is equipped with an init/fini and ctor/dtor
 * pair, as well as with its own set of small per-CPU caches, layered above
 * the Zone's general Bucket cache.
 *
 * The PCPU caches are protected by their own locks, while the Zones backed
 * by the same Keg all share a common Keg lock (to coalesce contention on
 * the backing slabs).  The backing Keg typically only serves one Zone but
 * in the case of multiple Zones, one of the Zones is considered the
 * Master Zone and all Zone-related stats from the Keg are done in the
 * Master Zone.  For an example of a Multi-Zone setup, refer to the
 * Mbuf allocation code.
 */

/*
 *	This is the representation for normal (Non OFFPAGE slab)
 *
 *	i == item
 *	s == slab pointer
 *
 *	<----------------  Page (UMA_SLAB_SIZE) ------------------>
 *	___________________________________________________________
 *     | _  _  _  _  _  _  _  _  _  _  _  _  _  _  _   ___________ |
 *     ||i||i||i||i||i||i||i||i||i||i||i||i||i||i||i| |slab header||
 *     ||_||_||_||_||_||_||_||_||_||_||_||_||_||_||_| |___________||
 *     |___________________________________________________________|
 *
 *
 *	This is an OFFPAGE slab. These can be larger than UMA_SLAB_SIZE.
 *
 *	___________________________________________________________
 *     | _  _  _  _  _  _  _  _  _  _  _  _  _  _  _  _  _  _  _   |
 *     ||i||i||i||i||i||i||i||i||i||i||i||i||i||i||i||i||i||i||i|  |
 *     ||_||_||_||_||_||_||_||_||_||_||_||_||_||_||_||_||_||_||_|  |
 *     |___________________________________________________________|
 *       ___________    ^
 *	|slab header|   |
 *	|___________|---*
 *
 */

#ifndef VM_UMA_INT_H
#define VM_UMA_INT_H

#define UMA_SLAB_SIZE	PAGE_SIZE	/* How big are our slabs? */
#define UMA_SLAB_MASK	(PAGE_SIZE - 1)	/* Mask to get back to the page */
#define UMA_SLAB_SHIFT	PAGE_SHIFT	/* Number of bits PAGE_MASK */

#define UMA_BOOT_PAGES		40	/* Pages allocated for startup */

/* Max waste before going to off page slab management */
#define UMA_MAX_WASTE	(UMA_SLAB_SIZE / 10)

/*
 * I doubt there will be many cases where this is exceeded. This is the initial
 * size of the hash table for uma_slabs that are managed off page. This hash
 * does expand by powers of two.  Currently it doesn't get smaller.
 */
#define UMA_HASH_SIZE_INIT	32

/*
 * I should investigate other hashing algorithms.  This should yield a low
 * number of collisions if the pages are relatively contiguous.
 *
 * This is the same algorithm that most processor caches use.
 *
 * I'm shifting and masking instead of % because it should be faster.
 */

#define UMA_HASH(h, s) ((((unsigned long)s) >> UMA_SLAB_SHIFT) &	\
    (h)->uh_hashmask)

#define UMA_HASH_INSERT(h, s, mem)					\
		SLIST_INSERT_HEAD(&(h)->uh_slab_hash[UMA_HASH((h),	\
		    (mem))], (s), us_hlink);
#define UMA_HASH_REMOVE(h, s, mem)					\
		SLIST_REMOVE(&(h)->uh_slab_hash[UMA_HASH((h),		\
		    (mem))], (s), uma_slab, us_hlink);

/* Hash table for freed address -> slab translation */

SLIST_HEAD(slabhead, uma_slab);

struct uma_hash {
	struct slabhead	*uh_slab_hash;	/* Hash table for slabs */
	int		uh_hashsize;	/* Current size of the hash table */
	int		uh_hashmask;	/* Mask used during hashing */
};

/*
 * Structures for per cpu queues.
 */

struct uma_bucket {
	LIST_ENTRY(uma_bucket)	ub_link;	/* Link into the zone */
	int16_t	ub_cnt;				/* Count of free items. */
	int16_t	ub_entries;			/* Max items. */
	void	*ub_bucket[];			/* actual allocation storage */
};

typedef struct uma_bucket * uma_bucket_t;

struct uma_cache {
	uma_bucket_t	uc_freebucket;	/* Bucket we're freeing to */
	uma_bucket_t	uc_allocbucket;	/* Bucket to allocate from */
	u_int64_t	uc_allocs;	/* Count of allocations */
};

typedef struct uma_cache * uma_cache_t;

/*
 * Keg management structure
 *
 * TODO: Optimize for cache line size
 *
 */
struct uma_keg {
	LIST_ENTRY(uma_keg)	uk_link;	/* List of all kegs */

	struct mtx	uk_lock;	/* Lock for the keg */
	struct uma_hash	uk_hash;

	LIST_HEAD(,uma_zone)	uk_zones;	/* Keg's zones */
	LIST_HEAD(,uma_slab)	uk_part_slab;	/* partially allocated slabs */
	LIST_HEAD(,uma_slab)	uk_free_slab;	/* empty slab list */
	LIST_HEAD(,uma_slab)	uk_full_slab;	/* full slabs */

	u_int32_t	uk_recurse;	/* Allocation recursion count */
	u_int32_t	uk_align;	/* Alignment mask */
	u_int32_t	uk_pages;	/* Total page count */
	u_int32_t	uk_free;	/* Count of items free in slabs */
	u_int32_t	uk_size;	/* Requested size of each item */
	u_int32_t	uk_rsize;	/* Real size of each item */
	u_int32_t	uk_maxpages;	/* Maximum number of pages to alloc */

	uma_init	uk_init;	/* Keg's init routine */
	uma_fini	uk_fini;	/* Keg's fini routine */
	uma_alloc	uk_allocf;	/* Allocation function */
	uma_free	uk_freef;	/* Free routine */

	struct vm_object	*uk_obj;	/* Zone specific object */
	vm_offset_t	uk_kva;		/* Base kva for zones with objs */
	uma_zone_t	uk_slabzone;	/* Slab zone backing us, if OFFPAGE */

	u_int16_t	uk_pgoff;	/* Offset to uma_slab struct */
	u_int16_t	uk_ppera;	/* pages per allocation from backend */
	u_int16_t	uk_ipers;	/* Items per slab */
	u_int16_t	uk_flags;	/* Internal flags */
};

/* Simpler reference to uma_keg for internal use. */
typedef struct uma_keg * uma_keg_t;

/* Page management structure */

/* Sorry for the union, but space efficiency is important */
struct uma_slab_head {
	uma_keg_t	us_keg;			/* Keg we live in */
	union {
		LIST_ENTRY(uma_slab)	_us_link;	/* slabs in zone */
		unsigned long	_us_size;	/* Size of allocation */
	} us_type;
	SLIST_ENTRY(uma_slab)	us_hlink;	/* Link for hash table */
	u_int8_t	*us_data;		/* First item */
	u_int8_t	us_flags;		/* Page flags see uma.h */
	u_int8_t	us_freecount;	/* How many are free? */
	u_int8_t	us_firstfree;	/* First free item index */
};

/* The standard slab structure */
struct uma_slab {
	struct uma_slab_head	us_head;	/* slab header data */
	struct {
		u_int8_t	us_item;
	} us_freelist[1];			/* actual number bigger */
};

/*
 * The slab structure for UMA_ZONE_REFCNT zones for whose items we
 * maintain reference counters in the slab for.
 */
struct uma_slab_refcnt {
	struct uma_slab_head	us_head;	/* slab header data */
	struct {
		u_int8_t	us_item;
		u_int32_t	us_refcnt;
	} us_freelist[1];			/* actual number bigger */
};

#define	us_keg		us_head.us_keg
#define	us_link		us_head.us_type._us_link
#define	us_size		us_head.us_type._us_size
#define	us_hlink	us_head.us_hlink
#define	us_data		us_head.us_data
#define	us_flags	us_head.us_flags
#define	us_freecount	us_head.us_freecount
#define	us_firstfree	us_head.us_firstfree

typedef struct uma_slab * uma_slab_t;
typedef struct uma_slab_refcnt * uma_slabrefcnt_t;

/*
 * These give us the size of one free item reference within our corresponding
 * uma_slab structures, so that our calculations during zone setup are correct
 * regardless of what the compiler decides to do with padding the structure
 * arrays within uma_slab.
 */
#define	UMA_FRITM_SZ	(sizeof(struct uma_slab) - sizeof(struct uma_slab_head))
#define	UMA_FRITMREF_SZ	(sizeof(struct uma_slab_refcnt) -	\
    sizeof(struct uma_slab_head))

/*
 * Zone management structure
 *
 * TODO: Optimize for cache line size
 *
 */
struct uma_zone {
	char		*uz_name;	/* Text name of the zone */
	struct mtx	*uz_lock;	/* Lock for the zone (keg's lock) */
	uma_keg_t	uz_keg;		/* Our underlying Keg */

	LIST_ENTRY(uma_zone)	uz_link;	/* List of all zones in keg */
	LIST_HEAD(,uma_bucket)	uz_full_bucket;	/* full buckets */
	LIST_HEAD(,uma_bucket)	uz_free_bucket;	/* Buckets for frees */

	uma_ctor	uz_ctor;	/* Constructor for each allocation */
	uma_dtor	uz_dtor;	/* Destructor */
	uma_init	uz_init;	/* Initializer for each item */
	uma_fini	uz_fini;	/* Discards memory */

	u_int64_t	uz_allocs;	/* Total number of allocations */
	uint16_t	uz_fills;	/* Outstanding bucket fills */
	uint16_t	uz_count;	/* Highest value ub_ptr can have */

	/*
	 * This HAS to be the last item because we adjust the zone size
	 * based on NCPU and then allocate the space for the zones.
	 */
	struct uma_cache	uz_cpu[1];	/* Per cpu caches */
};

/*
 * These flags must not overlap with the UMA_ZONE flags specified in uma.h.
 */
#define UMA_ZFLAG_PRIVALLOC	0x1000		/* Use uz_allocf. */
#define UMA_ZFLAG_INTERNAL	0x2000		/* No offpage no PCPU. */
#define UMA_ZFLAG_FULL		0x4000		/* Reached uz_maxpages */
#define UMA_ZFLAG_CACHEONLY	0x8000		/* Don't ask VM for buckets. */

/* Internal prototypes */
static __inline uma_slab_t hash_sfind(struct uma_hash *hash, u_int8_t *data);
void *uma_large_malloc(int size, int wait);
void uma_large_free(uma_slab_t slab);

/* Lock Macros */

#define	ZONE_LOCK_INIT(z, lc)					\
	do {							\
		if ((lc))					\
			mtx_init((z)->uz_lock, (z)->uz_name,	\
			    (z)->uz_name, MTX_DEF | MTX_DUPOK);	\
		else						\
			mtx_init((z)->uz_lock, (z)->uz_name,	\
			    "UMA zone", MTX_DEF | MTX_DUPOK);	\
	} while (0)

#define	ZONE_LOCK_FINI(z)	mtx_destroy((z)->uz_lock)
#define	ZONE_LOCK(z)	mtx_lock((z)->uz_lock)
#define ZONE_UNLOCK(z)	mtx_unlock((z)->uz_lock)

#define	CPU_LOCK_INIT(cpu)					\
	mtx_init(&uma_pcpu_mtx[(cpu)], "UMA pcpu", "UMA pcpu",	\
	    MTX_DEF | MTX_DUPOK)

#define CPU_LOCK(cpu)						\
	mtx_lock(&uma_pcpu_mtx[(cpu)])

#define CPU_UNLOCK(cpu)						\
	mtx_unlock(&uma_pcpu_mtx[(cpu)])

/*
 * Find a slab within a hash table.  This is used for OFFPAGE zones to lookup
 * the slab structure.
 *
 * Arguments:
 *	hash  The hash table to search.
 *	data  The base page of the item.
 *
 * Returns:
 *	A pointer to a slab if successful, else NULL.
 */
static __inline uma_slab_t
hash_sfind(struct uma_hash *hash, u_int8_t *data)
{
        uma_slab_t slab;
        int hval;

        hval = UMA_HASH(hash, data);

        SLIST_FOREACH(slab, &hash->uh_slab_hash[hval], us_hlink) {
                if ((u_int8_t *)slab->us_data == data)
                        return (slab);
        }
        return (NULL);
}

static __inline uma_slab_t
vtoslab(vm_offset_t va)
{
	vm_page_t p;
	uma_slab_t slab;

	p = PHYS_TO_VM_PAGE(pmap_kextract(va));
	slab = (uma_slab_t )p->object;

	if (p->flags & PG_SLAB)
		return (slab);
	else
		return (NULL);
}

static __inline void
vsetslab(vm_offset_t va, uma_slab_t slab)
{
	vm_page_t p;

	p = PHYS_TO_VM_PAGE(pmap_kextract(va));
	p->object = (vm_object_t)slab;
	p->flags |= PG_SLAB;
}

static __inline void
vsetobj(vm_offset_t va, vm_object_t obj)
{
	vm_page_t p;

	p = PHYS_TO_VM_PAGE(pmap_kextract(va));
	p->object = obj;
	p->flags &= ~PG_SLAB;
}

/*
 * The following two functions may be defined by architecture specific code
 * if they can provide more effecient allocation functions.  This is useful
 * for using direct mapped addresses.
 */
void *uma_small_alloc(uma_zone_t zone, int bytes, u_int8_t *pflag, int wait);
void uma_small_free(void *mem, int size, u_int8_t flags);

#endif /* VM_UMA_INT_H */