/*- * 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 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 __FBSDID("$FreeBSD$"); #include "opt_ddb.h" #include #include #include #include #include #include /* smr.h depends on struct thread. */ #include #include #ifdef DDB #include #endif #define PCTRIE_MASK (PCTRIE_COUNT - 1) #define PCTRIE_LIMIT (howmany(sizeof(uint64_t) * NBBY, PCTRIE_WIDTH) - 1) #if PCTRIE_WIDTH == 3 typedef uint8_t pn_popmap_t; #elif PCTRIE_WIDTH == 4 typedef uint16_t pn_popmap_t; #elif PCTRIE_WIDTH == 5 typedef uint32_t pn_popmap_t; #else #error Unsupported width #endif _Static_assert(sizeof(pn_popmap_t) <= sizeof(int), "pn_popmap_t too wide"); /* Flag bits stored in node pointers. */ #define PCTRIE_ISLEAF 0x1 #define PCTRIE_FLAGS 0x1 #define PCTRIE_PAD PCTRIE_FLAGS /* Returns one unit associated with specified level. */ #define PCTRIE_UNITLEVEL(lev) \ ((uint64_t)1 << ((lev) * PCTRIE_WIDTH)) struct pctrie_node; typedef SMR_POINTER(struct pctrie_node *) smr_pctnode_t; struct pctrie_node { uint64_t pn_owner; /* Owner of record. */ pn_popmap_t pn_popmap; /* Valid children. */ uint8_t pn_clev; /* Current level. */ smr_pctnode_t pn_child[PCTRIE_COUNT]; /* Child nodes. */ }; enum pctrie_access { PCTRIE_SMR, PCTRIE_LOCKED, PCTRIE_UNSERIALIZED }; static __inline void pctrie_node_store(smr_pctnode_t *p, void *val, enum pctrie_access access); /* * Return the position in the array for a given level. */ static __inline int pctrie_slot(uint64_t index, uint16_t level) { return ((index >> (level * PCTRIE_WIDTH)) & PCTRIE_MASK); } /* Computes the key (index) with the low-order 'level' radix-digits zeroed. */ static __inline uint64_t pctrie_trimkey(uint64_t index, uint16_t level) { return (index & -PCTRIE_UNITLEVEL(level)); } /* * Allocate a node. Pre-allocation should ensure that the request * will always be satisfied. */ static struct pctrie_node * pctrie_node_get(struct pctrie *ptree, pctrie_alloc_t allocfn, uint64_t index, uint16_t clevel) { struct pctrie_node *node; node = allocfn(ptree); if (node == 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 (node->pn_popmap != 0) { pctrie_node_store(&node->pn_child[ffs(node->pn_popmap) - 1], NULL, PCTRIE_UNSERIALIZED); node->pn_popmap = 0; } node->pn_owner = pctrie_trimkey(index, clevel + 1); node->pn_clev = clevel; return (node); } /* * Free radix node. */ static __inline void pctrie_node_put(struct pctrie *ptree, struct pctrie_node *node, pctrie_free_t freefn) { #ifdef INVARIANTS int slot; KASSERT(powerof2(node->pn_popmap), ("pctrie_node_put: node %p has too many children %04x", node, node->pn_popmap)); for (slot = 0; slot < PCTRIE_COUNT; slot++) { if ((node->pn_popmap & (1 << slot)) != 0) continue; KASSERT(smr_unserialized_load(&node->pn_child[slot], true) == NULL, ("pctrie_node_put: node %p has a child", node)); } #endif freefn(ptree, node); } /* * Fetch a node pointer from a slot. */ static __inline struct pctrie_node * pctrie_node_load(smr_pctnode_t *p, smr_t smr, enum pctrie_access access) { switch (access) { case PCTRIE_UNSERIALIZED: return (smr_unserialized_load(p, true)); case PCTRIE_LOCKED: return (smr_serialized_load(p, true)); case PCTRIE_SMR: return (smr_entered_load(p, smr)); } __assert_unreachable(); } static __inline void pctrie_node_store(smr_pctnode_t *p, void *v, enum pctrie_access access) { switch (access) { case PCTRIE_UNSERIALIZED: smr_unserialized_store(p, v, true); break; case PCTRIE_LOCKED: smr_serialized_store(p, v, true); break; case PCTRIE_SMR: panic("%s: Not supported in SMR section.", __func__); break; default: __assert_unreachable(); break; } } /* * Get the root node for a tree. */ static __inline struct pctrie_node * pctrie_root_load(struct pctrie *ptree, smr_t smr, enum pctrie_access access) { return (pctrie_node_load((smr_pctnode_t *)&ptree->pt_root, smr, access)); } /* * Set the root node for a tree. */ static __inline void pctrie_root_store(struct pctrie *ptree, struct pctrie_node *node, enum pctrie_access access) { pctrie_node_store((smr_pctnode_t *)&ptree->pt_root, node, access); } /* * Returns TRUE if the specified node is a leaf and FALSE otherwise. */ static __inline bool pctrie_isleaf(struct pctrie_node *node) { return (((uintptr_t)node & PCTRIE_ISLEAF) != 0); } /* * Returns val with leaf bit set. */ static __inline void * pctrie_toleaf(uint64_t *val) { return ((void *)((uintptr_t)val | PCTRIE_ISLEAF)); } /* * Returns the associated val extracted from node. */ static __inline uint64_t * pctrie_toval(struct pctrie_node *node) { return ((uint64_t *)((uintptr_t)node & ~PCTRIE_FLAGS)); } /* * Make 'child' a child of 'node'. */ static __inline void pctrie_addnode(struct pctrie_node *node, uint64_t index, uint16_t clev, struct pctrie_node *child, enum pctrie_access access) { int slot; slot = pctrie_slot(index, clev); pctrie_node_store(&node->pn_child[slot], child, access); node->pn_popmap ^= 1 << slot; KASSERT((node->pn_popmap & (1 << slot)) != 0, ("%s: bad popmap slot %d in node %p", __func__, slot, node)); } /* * Returns the level where two keys differ. * It cannot accept 2 equal keys. */ static __inline uint16_t pctrie_keydiff(uint64_t index1, uint64_t index2) { KASSERT(index1 != index2, ("%s: passing the same key value %jx", __func__, (uintmax_t)index1)); CTASSERT(sizeof(long long) >= sizeof(uint64_t)); /* * From the highest-order bit where the indexes differ, * compute the highest level in the trie where they differ. */ return ((flsll(index1 ^ index2) - 1) / PCTRIE_WIDTH); } /* * Returns TRUE if it can be determined that key does not belong to the * specified node. Otherwise, returns FALSE. */ static __inline bool pctrie_keybarr(struct pctrie_node *node, uint64_t idx) { if (node->pn_clev < PCTRIE_LIMIT) { idx = pctrie_trimkey(idx, node->pn_clev + 1); return (idx != node->pn_owner); } return (false); } /* * Internal helper for pctrie_reclaim_allnodes(). * This function is recursive. */ static void pctrie_reclaim_allnodes_int(struct pctrie *ptree, struct pctrie_node *node, pctrie_free_t freefn) { struct pctrie_node *child; int slot; while (node->pn_popmap != 0) { slot = ffs(node->pn_popmap) - 1; child = pctrie_node_load(&node->pn_child[slot], NULL, PCTRIE_UNSERIALIZED); KASSERT(child != NULL, ("%s: bad popmap slot %d in node %p", __func__, slot, node)); if (!pctrie_isleaf(child)) pctrie_reclaim_allnodes_int(ptree, child, freefn); node->pn_popmap ^= 1 << slot; pctrie_node_store(&node->pn_child[slot], NULL, PCTRIE_UNSERIALIZED); } pctrie_node_put(ptree, node, freefn); } /* * pctrie node zone initializer. */ int pctrie_zone_init(void *mem, int size __unused, int flags __unused) { struct pctrie_node *node; node = mem; node->pn_popmap = 0; memset(node->pn_child, 0, sizeof(node->pn_child)); return (0); } size_t pctrie_node_size(void) { return (sizeof(struct pctrie_node)); } /* * Inserts the key-value pair into the trie. * Panics if the key already exists. */ int pctrie_insert(struct pctrie *ptree, uint64_t *val, pctrie_alloc_t allocfn) { uint64_t index, newind; struct pctrie_node *leaf, *node, *tmp; smr_pctnode_t *parentp; int slot; uint16_t clev; index = *val; leaf = pctrie_toleaf(val); /* * The owner of record for root is not really important because it * will never be used. */ node = pctrie_root_load(ptree, NULL, PCTRIE_LOCKED); if (node == NULL) { ptree->pt_root = (uintptr_t)leaf; return (0); } for (parentp = (smr_pctnode_t *)&ptree->pt_root;; node = tmp) { if (pctrie_isleaf(node)) { newind = *pctrie_toval(node); if (newind == index) panic("%s: key %jx is already present", __func__, (uintmax_t)index); break; } else if (pctrie_keybarr(node, index)) { newind = node->pn_owner; break; } slot = pctrie_slot(index, node->pn_clev); parentp = &node->pn_child[slot]; tmp = pctrie_node_load(parentp, NULL, PCTRIE_LOCKED); if (tmp == NULL) { pctrie_addnode(node, index, node->pn_clev, leaf, PCTRIE_LOCKED); return (0); } } /* * 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. */ clev = pctrie_keydiff(newind, index); tmp = pctrie_node_get(ptree, allocfn, index, clev); if (tmp == NULL) return (ENOMEM); /* These writes are not yet visible due to ordering. */ pctrie_addnode(tmp, index, clev, leaf, PCTRIE_UNSERIALIZED); pctrie_addnode(tmp, newind, clev, node, PCTRIE_UNSERIALIZED); /* Synchronize to make the above visible. */ pctrie_node_store(parentp, tmp, PCTRIE_LOCKED); return (0); } /* * Returns the value stored at the index. If the index is not present, * NULL is returned. */ static __always_inline uint64_t * _pctrie_lookup(struct pctrie *ptree, uint64_t index, smr_t smr, enum pctrie_access access) { struct pctrie_node *node; uint64_t *m; int slot; node = pctrie_root_load(ptree, smr, access); while (node != NULL) { if (pctrie_isleaf(node)) { m = pctrie_toval(node); if (*m == index) return (m); break; } if (pctrie_keybarr(node, index)) break; slot = pctrie_slot(index, node->pn_clev); node = pctrie_node_load(&node->pn_child[slot], smr, access); } return (NULL); } /* * Returns the value stored at the index, assuming access is externally * synchronized by a lock. * * If the index is not present, NULL is returned. */ uint64_t * pctrie_lookup(struct pctrie *ptree, uint64_t index) { return (_pctrie_lookup(ptree, index, NULL, PCTRIE_LOCKED)); } /* * Returns the value stored at the index without requiring an external lock. * * If the index is not present, NULL is returned. */ uint64_t * pctrie_lookup_unlocked(struct pctrie *ptree, uint64_t index, smr_t smr) { uint64_t *res; smr_enter(smr); res = _pctrie_lookup(ptree, index, smr, PCTRIE_SMR); smr_exit(smr); return (res); } /* * Returns the value with the least index that is greater than or equal to the * specified index, or NULL if there are no such values. * * Requires that access be externally synchronized by a lock. */ uint64_t * pctrie_lookup_ge(struct pctrie *ptree, uint64_t index) { struct pctrie_node *node, *succ; uint64_t *m; int slot; /* * Descend the trie as if performing an ordinary lookup for the * specified value. 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 least value that is both * outside our current path down the trie and greater than the specified * index resides. (The node's popmap makes it fast and easy to * recognize a branching-off point.) If our ordinary lookup fails to * yield a value that is greater than or equal to the specified index, * 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. */ node = pctrie_root_load(ptree, NULL, PCTRIE_LOCKED); succ = NULL; while (node != NULL) { if (pctrie_isleaf(node)) { m = pctrie_toval(node); if (*m >= index) return (m); break; } if (pctrie_keybarr(node, index)) { /* * If all values in this subtree are > index, then the * least value in this subtree is the answer. */ if (node->pn_owner > index) succ = node; break; } slot = pctrie_slot(index, node->pn_clev); /* * Just in case the next search step leads to a subtree of all * values < index, check popmap to see if a next bigger step, to * a subtree of all pages with values > index, is available. If * so, remember to restart the search here. */ if ((node->pn_popmap >> slot) > 1) succ = node; node = pctrie_node_load(&node->pn_child[slot], NULL, PCTRIE_LOCKED); } /* * Restart the search from the last place visited in the subtree that * included some values > index, if there was such a place. */ if (succ == NULL) return (NULL); if (succ != node) { /* * Take a step to the next bigger sibling of the node chosen * last time. In that subtree, all values > index. */ slot = pctrie_slot(index, succ->pn_clev) + 1; KASSERT((succ->pn_popmap >> slot) != 0, ("%s: no popmap siblings past slot %d in node %p", __func__, slot, succ)); slot += ffs(succ->pn_popmap >> slot) - 1; succ = pctrie_node_load(&succ->pn_child[slot], NULL, PCTRIE_LOCKED); } /* * Find the value in the subtree rooted at "succ" with the least index. */ while (!pctrie_isleaf(succ)) { KASSERT(succ->pn_popmap != 0, ("%s: no popmap children in node %p", __func__, succ)); slot = ffs(succ->pn_popmap) - 1; succ = pctrie_node_load(&succ->pn_child[slot], NULL, PCTRIE_LOCKED); } return (pctrie_toval(succ)); } /* * Returns the value with the greatest index that is less than or equal to the * specified index, or NULL if there are no such values. * * Requires that access be externally synchronized by a lock. */ uint64_t * pctrie_lookup_le(struct pctrie *ptree, uint64_t index) { struct pctrie_node *node, *pred; uint64_t *m; int slot; /* * Mirror the implementation of pctrie_lookup_ge, described above. */ node = pctrie_root_load(ptree, NULL, PCTRIE_LOCKED); pred = NULL; while (node != NULL) { if (pctrie_isleaf(node)) { m = pctrie_toval(node); if (*m <= index) return (m); break; } if (pctrie_keybarr(node, index)) { if (node->pn_owner < index) pred = node; break; } slot = pctrie_slot(index, node->pn_clev); if ((node->pn_popmap & ((1 << slot) - 1)) != 0) pred = node; node = pctrie_node_load(&node->pn_child[slot], NULL, PCTRIE_LOCKED); } if (pred == NULL) return (NULL); if (pred != node) { slot = pctrie_slot(index, pred->pn_clev); KASSERT((pred->pn_popmap & ((1 << slot) - 1)) != 0, ("%s: no popmap siblings before slot %d in node %p", __func__, slot, pred)); slot = fls(pred->pn_popmap & ((1 << slot) - 1)) - 1; pred = pctrie_node_load(&pred->pn_child[slot], NULL, PCTRIE_LOCKED); } while (!pctrie_isleaf(pred)) { KASSERT(pred->pn_popmap != 0, ("%s: no popmap children in node %p", __func__, pred)); slot = fls(pred->pn_popmap) - 1; pred = pctrie_node_load(&pred->pn_child[slot], NULL, PCTRIE_LOCKED); } return (pctrie_toval(pred)); } /* * Remove the specified index from the tree. * Panics if the key is not present. */ void pctrie_remove(struct pctrie *ptree, uint64_t index, pctrie_free_t freefn) { struct pctrie_node *node, *parent, *tmp; uint64_t *m; int slot; node = pctrie_root_load(ptree, NULL, PCTRIE_LOCKED); if (pctrie_isleaf(node)) { m = pctrie_toval(node); if (*m != index) panic("%s: invalid key found", __func__); pctrie_root_store(ptree, NULL, PCTRIE_LOCKED); return; } parent = NULL; for (;;) { if (node == NULL) panic("pctrie_remove: impossible to locate the key"); slot = pctrie_slot(index, node->pn_clev); tmp = pctrie_node_load(&node->pn_child[slot], NULL, PCTRIE_LOCKED); if (pctrie_isleaf(tmp)) { m = pctrie_toval(tmp); if (*m != index) panic("%s: invalid key found", __func__); KASSERT((node->pn_popmap & (1 << slot)) != 0, ("%s: bad popmap slot %d in node %p", __func__, slot, node)); node->pn_popmap ^= 1 << slot; pctrie_node_store(&node->pn_child[slot], NULL, PCTRIE_LOCKED); if (!powerof2(node->pn_popmap)) break; KASSERT(node->pn_popmap != 0, ("%s: bad popmap all zeroes", __func__)); slot = ffs(node->pn_popmap) - 1; tmp = pctrie_node_load(&node->pn_child[slot], NULL, PCTRIE_LOCKED); KASSERT(tmp != NULL, ("%s: bad popmap slot %d in node %p", __func__, slot, node)); if (parent == NULL) pctrie_root_store(ptree, tmp, PCTRIE_LOCKED); else { slot = pctrie_slot(index, parent->pn_clev); KASSERT(pctrie_node_load( &parent->pn_child[slot], NULL, PCTRIE_LOCKED) == node, ("%s: invalid child value", __func__)); pctrie_node_store(&parent->pn_child[slot], tmp, PCTRIE_LOCKED); } /* * The child is still valid and we can not zero the * pointer until all SMR references are gone. */ pctrie_node_put(ptree, node, freefn); break; } parent = node; node = tmp; } } /* * Remove and free all the nodes from the tree. * This function is recursive but there is a tight control on it as the * maximum depth of the tree is fixed. */ void pctrie_reclaim_allnodes(struct pctrie *ptree, pctrie_free_t freefn) { struct pctrie_node *root; root = pctrie_root_load(ptree, NULL, PCTRIE_LOCKED); if (root == NULL) return; pctrie_root_store(ptree, NULL, PCTRIE_UNSERIALIZED); if (!pctrie_isleaf(root)) pctrie_reclaim_allnodes_int(ptree, root, freefn); } #ifdef DDB /* * Show details about the given node. */ DB_SHOW_COMMAND(pctrienode, db_show_pctrienode) { struct pctrie_node *node, *tmp; int slot; pn_popmap_t popmap; if (!have_addr) return; node = (struct pctrie_node *)addr; db_printf("node %p, owner %jx, children popmap %04x, level %u:\n", (void *)node, (uintmax_t)node->pn_owner, node->pn_popmap, node->pn_clev); for (popmap = node->pn_popmap; popmap != 0; popmap ^= 1 << slot) { slot = ffs(popmap) - 1; tmp = pctrie_node_load(&node->pn_child[slot], NULL, PCTRIE_UNSERIALIZED); db_printf("slot: %d, val: %p, value: %p, clev: %d\n", slot, (void *)tmp, pctrie_isleaf(tmp) ? pctrie_toval(tmp) : NULL, node->pn_clev); } } #endif /* DDB */