/*- * SPDX-License-Identifier: BSD-2-Clause * * Copyright (c) 2013 EMC Corp. * Copyright (c) 2011 Jeffrey Roberson * Copyright (c) 2008 Mayur Shardul * 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, 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 AND CONTRIBUTORS ``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 OR CONTRIBUTORS 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. * */ /* * Path-compressed radix trie implementation. * The following code is not generalized into a general purpose library * because there are way too many parameters embedded that should really * be decided by the library consumers. At the same time, consumers * of this code must achieve highest possible performance. * * The implementation takes into account the following rationale: * - Size of the nodes should be as small as possible but still big enough * to avoid a large maximum depth for the trie. This is a balance * between the necessity to not wire too much physical memory for the nodes * and the necessity to avoid too much cache pollution during the trie * operations. * - There is not a huge bias toward the number of lookup operations over * the number of insert and remove operations. This basically implies * that optimizations supposedly helping one operation but hurting the * other might be carefully evaluated. * - On average not many nodes are expected to be fully populated, hence * level compression may just complicate things. */ #include #include "opt_ddb.h" #include #include #include #include #include #include #include #include #include #include #include #include #include #include #ifdef DDB #include #endif /* * These widths should allow the pointers to a node's children to fit within * a single cache line. The extra levels from a narrow width should not be * a problem thanks to path compression. */ #ifdef __LP64__ #define VM_RADIX_WIDTH 4 #else #define VM_RADIX_WIDTH 3 #endif #define VM_RADIX_COUNT (1 << VM_RADIX_WIDTH) #define VM_RADIX_MASK (VM_RADIX_COUNT - 1) #define VM_RADIX_LIMIT \ (howmany(sizeof(vm_pindex_t) * NBBY, VM_RADIX_WIDTH) - 1) #if VM_RADIX_WIDTH == 3 typedef uint8_t rn_popmap_t; #elif VM_RADIX_WIDTH == 4 typedef uint16_t rn_popmap_t; #elif VM_RADIX_WIDTH == 5 typedef uint32_t rn_popmap_t; #else #error Unsupported width #endif _Static_assert(sizeof(rn_popmap_t) <= sizeof(int), "rn_popmap_t too wide"); /* Set of all flag bits stored in node pointers. */ #define VM_RADIX_FLAGS (VM_RADIX_ISLEAF) #define VM_RADIX_PAD VM_RADIX_FLAGS enum vm_radix_access { SMR, LOCKED, UNSERIALIZED }; struct vm_radix_node; typedef SMR_POINTER(struct vm_radix_node *) smrnode_t; struct vm_radix_node { vm_pindex_t rn_owner; /* Owner of record. */ rn_popmap_t rn_popmap; /* Valid children. */ uint8_t rn_clev; /* Level * WIDTH. */ smrnode_t rn_child[VM_RADIX_COUNT]; /* Child nodes. */ }; static uma_zone_t vm_radix_node_zone; static smr_t vm_radix_smr; static void vm_radix_node_store(smrnode_t *p, struct vm_radix_node *v, enum vm_radix_access access); /* * Map index to an array position for the children of rnode, */ static __inline int vm_radix_slot(struct vm_radix_node *rnode, vm_pindex_t index) { return ((index >> rnode->rn_clev) & VM_RADIX_MASK); } /* * Returns true if index does not belong to the specified rnode. Otherwise, * sets slot value, and returns false. */ static __inline bool vm_radix_keybarr(struct vm_radix_node *rnode, vm_pindex_t index, int *slot) { index = (index - rnode->rn_owner) >> rnode->rn_clev; if (index >= VM_RADIX_COUNT) return (true); *slot = index; return (false); } /* * Allocate a radix node. */ static struct vm_radix_node * vm_radix_node_get(vm_pindex_t index, vm_pindex_t newind) { struct vm_radix_node *rnode; rnode = uma_zalloc_smr(vm_radix_node_zone, M_NOWAIT); if (rnode == NULL) return (NULL); /* * We want to clear the last child pointer after the final section * has exited so lookup can not return false negatives. It is done * here because it will be cache-cold in the dtor callback. */ if (rnode->rn_popmap != 0) { vm_radix_node_store(&rnode->rn_child[ffs(rnode->rn_popmap) - 1], VM_RADIX_NULL, UNSERIALIZED); rnode->rn_popmap = 0; } /* * From the highest-order bit where the indexes differ, * compute the highest level in the trie where they differ. Then, * compute the least index of this subtrie. */ KASSERT(index != newind, ("%s: passing the same key value %jx", __func__, (uintmax_t)index)); _Static_assert(sizeof(long long) >= sizeof(vm_pindex_t), "vm_pindex_t too wide"); _Static_assert(sizeof(vm_pindex_t) * NBBY <= (1 << (sizeof(rnode->rn_clev) * NBBY)), "rn_clev too narrow"); rnode->rn_clev = rounddown(flsll(index ^ newind) - 1, VM_RADIX_WIDTH); rnode->rn_owner = VM_RADIX_COUNT; rnode->rn_owner = index & -(rnode->rn_owner << rnode->rn_clev); return (rnode); } /* * Free radix node. */ static __inline void vm_radix_node_put(struct vm_radix_node *rnode) { #ifdef INVARIANTS int slot; KASSERT(powerof2(rnode->rn_popmap), ("vm_radix_node_put: rnode %p has too many children %04x", rnode, rnode->rn_popmap)); for (slot = 0; slot < VM_RADIX_COUNT; slot++) { if ((rnode->rn_popmap & (1 << slot)) != 0) continue; KASSERT(smr_unserialized_load(&rnode->rn_child[slot], true) == VM_RADIX_NULL, ("vm_radix_node_put: rnode %p has a child", rnode)); } #endif uma_zfree_smr(vm_radix_node_zone, rnode); } /* * Fetch a node pointer from a slot in another node. */ static __inline struct vm_radix_node * vm_radix_node_load(smrnode_t *p, enum vm_radix_access access) { switch (access) { case UNSERIALIZED: return (smr_unserialized_load(p, true)); case LOCKED: return (smr_serialized_load(p, true)); case SMR: return (smr_entered_load(p, vm_radix_smr)); } __assert_unreachable(); } static __inline void vm_radix_node_store(smrnode_t *p, struct vm_radix_node *v, enum vm_radix_access access) { switch (access) { case UNSERIALIZED: smr_unserialized_store(p, v, true); break; case LOCKED: smr_serialized_store(p, v, true); break; case SMR: panic("vm_radix_node_store: Not supported in smr section."); } } /* * Get the root node for a radix tree. */ static __inline struct vm_radix_node * vm_radix_root_load(struct vm_radix *rtree, enum vm_radix_access access) { return (vm_radix_node_load((smrnode_t *)&rtree->rt_root, access)); } /* * Set the root node for a radix tree. */ static __inline void vm_radix_root_store(struct vm_radix *rtree, struct vm_radix_node *rnode, enum vm_radix_access access) { vm_radix_node_store((smrnode_t *)&rtree->rt_root, rnode, access); } /* * Returns TRUE if the specified radix node is a leaf and FALSE otherwise. */ static __inline bool vm_radix_isleaf(struct vm_radix_node *rnode) { return (((uintptr_t)rnode & VM_RADIX_ISLEAF) != 0); } /* * Returns page cast to radix node with leaf bit set. */ static __inline struct vm_radix_node * vm_radix_toleaf(vm_page_t page) { return ((struct vm_radix_node *)((uintptr_t)page | VM_RADIX_ISLEAF)); } /* * Returns the associated page extracted from rnode. */ static __inline vm_page_t vm_radix_topage(struct vm_radix_node *rnode) { return ((vm_page_t)((uintptr_t)rnode & ~VM_RADIX_FLAGS)); } /* * Make 'child' a child of 'rnode'. */ static __inline void vm_radix_addnode(struct vm_radix_node *rnode, vm_pindex_t index, struct vm_radix_node *child, enum vm_radix_access access) { int slot; slot = vm_radix_slot(rnode, index); vm_radix_node_store(&rnode->rn_child[slot], child, access); rnode->rn_popmap ^= 1 << slot; KASSERT((rnode->rn_popmap & (1 << slot)) != 0, ("%s: bad popmap slot %d in rnode %p", __func__, slot, rnode)); } /* * Internal helper for vm_radix_reclaim_allnodes(). * This function is recursive. */ static void vm_radix_reclaim_allnodes_int(struct vm_radix_node *rnode) { struct vm_radix_node *child; int slot; while (rnode->rn_popmap != 0) { slot = ffs(rnode->rn_popmap) - 1; child = vm_radix_node_load(&rnode->rn_child[slot], UNSERIALIZED); KASSERT(child != VM_RADIX_NULL, ("%s: bad popmap slot %d in rnode %p", __func__, slot, rnode)); if (!vm_radix_isleaf(child)) vm_radix_reclaim_allnodes_int(child); rnode->rn_popmap ^= 1 << slot; vm_radix_node_store(&rnode->rn_child[slot], VM_RADIX_NULL, UNSERIALIZED); } vm_radix_node_put(rnode); } /* * radix node zone initializer. */ static int vm_radix_zone_init(void *mem, int size, int flags) { struct vm_radix_node *rnode; rnode = mem; rnode->rn_popmap = 0; for (int i = 0; i < nitems(rnode->rn_child); i++) vm_radix_node_store(&rnode->rn_child[i], VM_RADIX_NULL, UNSERIALIZED); return (0); } #ifndef UMA_MD_SMALL_ALLOC void vm_radix_reserve_kva(void); /* * Reserve the KVA necessary to satisfy the node allocation. * This is mandatory in architectures not supporting direct * mapping as they will need otherwise to carve into the kernel maps for * every node allocation, resulting into deadlocks for consumers already * working with kernel maps. */ void vm_radix_reserve_kva(void) { /* * Calculate the number of reserved nodes, discounting the pages that * are needed to store them. */ if (!uma_zone_reserve_kva(vm_radix_node_zone, ((vm_paddr_t)vm_cnt.v_page_count * PAGE_SIZE) / (PAGE_SIZE + sizeof(struct vm_radix_node)))) panic("%s: unable to reserve KVA", __func__); } #endif /* * Initialize the UMA slab zone. */ void vm_radix_zinit(void) { vm_radix_node_zone = uma_zcreate("RADIX NODE", sizeof(struct vm_radix_node), NULL, NULL, vm_radix_zone_init, NULL, VM_RADIX_PAD, UMA_ZONE_VM | UMA_ZONE_SMR); vm_radix_smr = uma_zone_get_smr(vm_radix_node_zone); } /* * Inserts the key-value pair into the trie. * Panics if the key already exists. */ int vm_radix_insert(struct vm_radix *rtree, vm_page_t page) { vm_pindex_t index, newind; struct vm_radix_node *leaf, *parent, *rnode; smrnode_t *parentp; int slot; index = page->pindex; leaf = vm_radix_toleaf(page); /* * The owner of record for root is not really important because it * will never be used. */ rnode = vm_radix_root_load(rtree, LOCKED); parent = NULL; for (;;) { if (vm_radix_isleaf(rnode)) { if (rnode == VM_RADIX_NULL) { if (parent == NULL) rtree->rt_root = leaf; else vm_radix_addnode(parent, index, leaf, LOCKED); return (0); } newind = vm_radix_topage(rnode)->pindex; if (newind == index) panic("%s: key %jx is already present", __func__, (uintmax_t)index); break; } if (vm_radix_keybarr(rnode, index, &slot)) { newind = rnode->rn_owner; break; } parent = rnode; rnode = vm_radix_node_load(&rnode->rn_child[slot], LOCKED); } /* * A new node is needed because the right insertion level is reached. * Setup the new intermediate node and add the 2 children: the * new object and the older edge or object. */ parentp = (parent != NULL) ? &parent->rn_child[slot]: (smrnode_t *)&rtree->rt_root; parent = vm_radix_node_get(index, newind); if (parent == NULL) return (ENOMEM); /* These writes are not yet visible due to ordering. */ vm_radix_addnode(parent, index, leaf, UNSERIALIZED); vm_radix_addnode(parent, newind, rnode, UNSERIALIZED); /* Serializing write to make the above visible. */ vm_radix_node_store(parentp, parent, LOCKED); return (0); } /* * Returns the value stored at the index. If the index is not present, * NULL is returned. */ static __always_inline vm_page_t _vm_radix_lookup(struct vm_radix *rtree, vm_pindex_t index, enum vm_radix_access access) { struct vm_radix_node *rnode; vm_page_t m; int slot; rnode = vm_radix_root_load(rtree, access); for (;;) { if (vm_radix_isleaf(rnode)) { if ((m = vm_radix_topage(rnode)) != NULL && m->pindex == index) return (m); break; } if (vm_radix_keybarr(rnode, index, &slot)) break; rnode = vm_radix_node_load(&rnode->rn_child[slot], access); } return (NULL); } /* * Returns the value stored at the index assuming there is an external lock. * * If the index is not present, NULL is returned. */ vm_page_t vm_radix_lookup(struct vm_radix *rtree, vm_pindex_t index) { return _vm_radix_lookup(rtree, index, LOCKED); } /* * Returns the value stored at the index without requiring an external lock. * * If the index is not present, NULL is returned. */ vm_page_t vm_radix_lookup_unlocked(struct vm_radix *rtree, vm_pindex_t index) { vm_page_t m; smr_enter(vm_radix_smr); m = _vm_radix_lookup(rtree, index, SMR); smr_exit(vm_radix_smr); return (m); } /* * Returns the page with the least pindex that is greater than or equal to the * specified pindex, or NULL if there are no such pages. * * Requires that access be externally synchronized by a lock. */ vm_page_t vm_radix_lookup_ge(struct vm_radix *rtree, vm_pindex_t index) { struct vm_radix_node *rnode, *succ; vm_page_t m; int slot; /* * Descend the trie as if performing an ordinary lookup for the page * with the specified pindex. However, unlike an ordinary lookup, as we * descend the trie, we use "succ" to remember the last branching-off * point, that is, the interior node under which the page with the least * pindex that is both outside our current path down the trie and more * than the specified pindex resides. (The node's popmap makes it fast * and easy to recognize a branching-off point.) If our ordinary lookup * fails to yield a page with a pindex that is greater than or equal to * the specified pindex, then we will exit this loop and perform a * lookup starting from "succ". If "succ" is not NULL, then that lookup * is guaranteed to succeed. */ rnode = vm_radix_root_load(rtree, LOCKED); succ = NULL; for (;;) { if (vm_radix_isleaf(rnode)) { if ((m = vm_radix_topage(rnode)) != NULL && m->pindex >= index) return (m); break; } if (vm_radix_keybarr(rnode, index, &slot)) { /* * If all pages in this subtree have pindex > index, * then the page in this subtree with the least pindex * is the answer. */ if (rnode->rn_owner > index) succ = rnode; break; } /* * Just in case the next search step leads to a subtree of all * pages with pindex < index, check popmap to see if a next * bigger step, to a subtree of all pages with pindex > index, * is available. If so, remember to restart the search here. */ if ((rnode->rn_popmap >> slot) > 1) succ = rnode; rnode = vm_radix_node_load(&rnode->rn_child[slot], LOCKED); } /* * Restart the search from the last place visited in the subtree that * included some pages with pindex > index, if there was such a place. */ if (succ == NULL) return (NULL); if (succ != rnode) { /* * Take a step to the next bigger sibling of the node chosen * last time. In that subtree, all pages have pindex > index. */ slot = vm_radix_slot(succ, index) + 1; KASSERT((succ->rn_popmap >> slot) != 0, ("%s: no popmap siblings past slot %d in node %p", __func__, slot, succ)); slot += ffs(succ->rn_popmap >> slot) - 1; succ = vm_radix_node_load(&succ->rn_child[slot], LOCKED); } /* * Find the page in the subtree rooted at "succ" with the least pindex. */ while (!vm_radix_isleaf(succ)) { KASSERT(succ->rn_popmap != 0, ("%s: no popmap children in node %p", __func__, succ)); slot = ffs(succ->rn_popmap) - 1; succ = vm_radix_node_load(&succ->rn_child[slot], LOCKED); } return (vm_radix_topage(succ)); } /* * Returns the page with the greatest pindex that is less than or equal to the * specified pindex, or NULL if there are no such pages. * * Requires that access be externally synchronized by a lock. */ vm_page_t vm_radix_lookup_le(struct vm_radix *rtree, vm_pindex_t index) { struct vm_radix_node *pred, *rnode; vm_page_t m; int slot; /* * Mirror the implementation of vm_radix_lookup_ge, described above. */ rnode = vm_radix_root_load(rtree, LOCKED); pred = NULL; for (;;) { if (vm_radix_isleaf(rnode)) { if ((m = vm_radix_topage(rnode)) != NULL && m->pindex <= index) return (m); break; } if (vm_radix_keybarr(rnode, index, &slot)) { if (rnode->rn_owner < index) pred = rnode; break; } if ((rnode->rn_popmap & ((1 << slot) - 1)) != 0) pred = rnode; rnode = vm_radix_node_load(&rnode->rn_child[slot], LOCKED); } if (pred == NULL) return (NULL); if (pred != rnode) { slot = vm_radix_slot(pred, index); KASSERT((pred->rn_popmap & ((1 << slot) - 1)) != 0, ("%s: no popmap siblings before slot %d in node %p", __func__, slot, pred)); slot = fls(pred->rn_popmap & ((1 << slot) - 1)) - 1; pred = vm_radix_node_load(&pred->rn_child[slot], LOCKED); } while (!vm_radix_isleaf(pred)) { KASSERT(pred->rn_popmap != 0, ("%s: no popmap children in node %p", __func__, pred)); slot = fls(pred->rn_popmap) - 1; pred = vm_radix_node_load(&pred->rn_child[slot], LOCKED); } return (vm_radix_topage(pred)); } /* * Remove the specified index from the trie, and return the value stored at * that index. If the index is not present, return NULL. */ vm_page_t vm_radix_remove(struct vm_radix *rtree, vm_pindex_t index) { struct vm_radix_node *child, *parent, *rnode; vm_page_t m; int slot; rnode = NULL; child = vm_radix_root_load(rtree, LOCKED); for (;;) { if (vm_radix_isleaf(child)) break; parent = rnode; rnode = child; slot = vm_radix_slot(rnode, index); child = vm_radix_node_load(&rnode->rn_child[slot], LOCKED); } if ((m = vm_radix_topage(child)) == NULL || m->pindex != index) return (NULL); if (rnode == NULL) { vm_radix_root_store(rtree, VM_RADIX_NULL, LOCKED); return (m); } KASSERT((rnode->rn_popmap & (1 << slot)) != 0, ("%s: bad popmap slot %d in rnode %p", __func__, slot, rnode)); rnode->rn_popmap ^= 1 << slot; vm_radix_node_store(&rnode->rn_child[slot], VM_RADIX_NULL, LOCKED); if (!powerof2(rnode->rn_popmap)) return (m); KASSERT(rnode->rn_popmap != 0, ("%s: bad popmap all zeroes", __func__)); slot = ffs(rnode->rn_popmap) - 1; child = vm_radix_node_load(&rnode->rn_child[slot], LOCKED); KASSERT(child != VM_RADIX_NULL, ("%s: bad popmap slot %d in rnode %p", __func__, slot, rnode)); if (parent == NULL) vm_radix_root_store(rtree, child, LOCKED); else { slot = vm_radix_slot(parent, index); KASSERT(rnode == vm_radix_node_load(&parent->rn_child[slot], LOCKED), ("%s: invalid child value", __func__)); vm_radix_node_store(&parent->rn_child[slot], child, LOCKED); } /* * The child is still valid and we can not zero the * pointer until all smr references are gone. */ vm_radix_node_put(rnode); return (m); } /* * Remove and free all the nodes from the radix tree. * This function is recursive but there is a tight control on it as the * maximum depth of the tree is fixed. */ void vm_radix_reclaim_allnodes(struct vm_radix *rtree) { struct vm_radix_node *root; root = vm_radix_root_load(rtree, LOCKED); if (root == VM_RADIX_NULL) return; vm_radix_root_store(rtree, VM_RADIX_NULL, UNSERIALIZED); if (!vm_radix_isleaf(root)) vm_radix_reclaim_allnodes_int(root); } /* * Replace an existing page in the trie with another one. * Panics if there is not an old page in the trie at the new page's index. */ vm_page_t vm_radix_replace(struct vm_radix *rtree, vm_page_t newpage) { struct vm_radix_node *leaf, *parent, *rnode; vm_page_t m; vm_pindex_t index; int slot; leaf = vm_radix_toleaf(newpage); index = newpage->pindex; rnode = vm_radix_root_load(rtree, LOCKED); parent = NULL; for (;;) { if (vm_radix_isleaf(rnode)) { if ((m = vm_radix_topage(rnode)) != NULL && m->pindex == index) { if (parent == NULL) rtree->rt_root = leaf; else vm_radix_node_store( &parent->rn_child[slot], leaf, LOCKED); return (m); } break; } if (vm_radix_keybarr(rnode, index, &slot)) break; parent = rnode; rnode = vm_radix_node_load(&rnode->rn_child[slot], LOCKED); } panic("%s: original replacing page not found", __func__); } void vm_radix_wait(void) { uma_zwait(vm_radix_node_zone); } #ifdef DDB /* * Show details about the given radix node. */ DB_SHOW_COMMAND(radixnode, db_show_radixnode) { struct vm_radix_node *rnode, *tmp; int slot; rn_popmap_t popmap; if (!have_addr) return; rnode = (struct vm_radix_node *)addr; db_printf("radixnode %p, owner %jx, children popmap %04x, level %u:\n", (void *)rnode, (uintmax_t)rnode->rn_owner, rnode->rn_popmap, rnode->rn_clev / VM_RADIX_WIDTH); for (popmap = rnode->rn_popmap; popmap != 0; popmap ^= 1 << slot) { slot = ffs(popmap) - 1; tmp = vm_radix_node_load(&rnode->rn_child[slot], UNSERIALIZED); db_printf("slot: %d, val: %p, page: %p, clev: %d\n", slot, (void *)tmp, vm_radix_isleaf(tmp) ? vm_radix_topage(tmp) : NULL, rnode->rn_clev / VM_RADIX_WIDTH); } } #endif /* DDB */