706 lines
17 KiB
C
706 lines
17 KiB
C
![]() |
/*
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* Copyright (c) 2013 EMC Corp.
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* Copyright (c) 2011 Jeffrey Roberson <jeff@freebsd.org>
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* Copyright (c) 2008 Mayur Shardul <mayur.shardul@gmail.com>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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*/
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/*
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* Path-compressed radix trie implementation.
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*
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* The implementation takes into account the following rationale:
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* - Size of the nodes should be as small as possible but still big enough
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* to avoid a large maximum depth for the trie. This is a balance
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* between the necessity to not wire too much physical memory for the nodes
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* and the necessity to avoid too much cache pollution during the trie
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* operations.
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* - There is not a huge bias toward the number of lookup operations over
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* the number of insert and remove operations. This basically implies
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* that optimizations supposedly helping one operation but hurting the
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* other might be carefully evaluated.
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* - On average not many nodes are expected to be fully populated, hence
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* level compression may just complicate things.
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include "opt_ddb.h"
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/kernel.h>
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#include <sys/pctrie.h>
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#ifdef DDB
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#include <ddb/ddb.h>
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#endif
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/*
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* These widths should allow the pointers to a node's children to fit within
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* a single cache line. The extra levels from a narrow width should not be
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* a problem thanks to path compression.
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*/
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#ifdef __LP64__
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#define PCTRIE_WIDTH 4
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#else
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#define PCTRIE_WIDTH 3
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#endif
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#define PCTRIE_COUNT (1 << PCTRIE_WIDTH)
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#define PCTRIE_MASK (PCTRIE_COUNT - 1)
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#define PCTRIE_LIMIT (howmany(sizeof(uint64_t) * NBBY, PCTRIE_WIDTH) - 1)
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/* Flag bits stored in node pointers. */
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#define PCTRIE_ISLEAF 0x1
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#define PCTRIE_FLAGS 0x1
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#define PCTRIE_PAD PCTRIE_FLAGS
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/* Returns one unit associated with specified level. */
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#define PCTRIE_UNITLEVEL(lev) \
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((uint64_t)1 << ((lev) * PCTRIE_WIDTH))
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struct pctrie_node {
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uint64_t pn_owner; /* Owner of record. */
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uint16_t pn_count; /* Valid children. */
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uint16_t pn_clev; /* Current level. */
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void *pn_child[PCTRIE_COUNT]; /* Child nodes. */
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};
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/*
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* Allocate a node. Pre-allocation should ensure that the request
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* will always be satisfied.
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*/
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static __inline struct pctrie_node *
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pctrie_node_get(struct pctrie *ptree, pctrie_alloc_t allocfn, uint64_t owner,
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uint16_t count, uint16_t clevel)
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{
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struct pctrie_node *node;
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node = allocfn(ptree);
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if (node == NULL)
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return (NULL);
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node->pn_owner = owner;
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node->pn_count = count;
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node->pn_clev = clevel;
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return (node);
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}
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/*
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* Free radix node.
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*/
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static __inline void
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pctrie_node_put(struct pctrie *ptree, struct pctrie_node *node,
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pctrie_free_t freefn)
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{
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#ifdef INVARIANTS
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int slot;
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KASSERT(node->pn_count == 0,
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("pctrie_node_put: node %p has %d children", node,
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node->pn_count));
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for (slot = 0; slot < PCTRIE_COUNT; slot++)
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KASSERT(node->pn_child[slot] == NULL,
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("pctrie_node_put: node %p has a child", node));
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#endif
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freefn(ptree, node);
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}
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/*
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* Return the position in the array for a given level.
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*/
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static __inline int
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pctrie_slot(uint64_t index, uint16_t level)
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{
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return ((index >> (level * PCTRIE_WIDTH)) & PCTRIE_MASK);
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}
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/* Trims the key after the specified level. */
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static __inline uint64_t
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pctrie_trimkey(uint64_t index, uint16_t level)
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{
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uint64_t ret;
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ret = index;
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if (level > 0) {
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ret >>= level * PCTRIE_WIDTH;
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ret <<= level * PCTRIE_WIDTH;
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}
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return (ret);
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}
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/*
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* Get the root node for a tree.
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*/
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static __inline struct pctrie_node *
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pctrie_getroot(struct pctrie *ptree)
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{
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return ((struct pctrie_node *)ptree->pt_root);
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}
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/*
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* Set the root node for a tree.
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*/
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static __inline void
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pctrie_setroot(struct pctrie *ptree, struct pctrie_node *node)
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{
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ptree->pt_root = (uintptr_t)node;
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}
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/*
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* Returns TRUE if the specified node is a leaf and FALSE otherwise.
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*/
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static __inline boolean_t
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pctrie_isleaf(struct pctrie_node *node)
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{
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return (((uintptr_t)node & PCTRIE_ISLEAF) != 0);
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}
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/*
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* Returns the associated val extracted from node.
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*/
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static __inline uint64_t *
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pctrie_toval(struct pctrie_node *node)
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{
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return ((uint64_t *)((uintptr_t)node & ~PCTRIE_FLAGS));
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}
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/*
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* Adds the val as a child of the provided node.
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*/
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static __inline void
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pctrie_addval(struct pctrie_node *node, uint64_t index, uint16_t clev,
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uint64_t *val)
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{
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int slot;
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slot = pctrie_slot(index, clev);
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node->pn_child[slot] = (void *)((uintptr_t)val | PCTRIE_ISLEAF);
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}
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/*
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* Returns the slot where two keys differ.
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* It cannot accept 2 equal keys.
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*/
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static __inline uint16_t
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pctrie_keydiff(uint64_t index1, uint64_t index2)
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{
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uint16_t clev;
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KASSERT(index1 != index2, ("%s: passing the same key value %jx",
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__func__, (uintmax_t)index1));
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index1 ^= index2;
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for (clev = PCTRIE_LIMIT;; clev--)
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if (pctrie_slot(index1, clev) != 0)
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return (clev);
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}
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/*
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* Returns TRUE if it can be determined that key does not belong to the
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* specified node. Otherwise, returns FALSE.
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*/
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static __inline boolean_t
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pctrie_keybarr(struct pctrie_node *node, uint64_t idx)
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{
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if (node->pn_clev < PCTRIE_LIMIT) {
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idx = pctrie_trimkey(idx, node->pn_clev + 1);
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return (idx != node->pn_owner);
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}
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return (FALSE);
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}
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/*
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* Internal helper for pctrie_reclaim_allnodes().
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* This function is recursive.
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*/
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static void
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pctrie_reclaim_allnodes_int(struct pctrie *ptree, struct pctrie_node *node,
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pctrie_free_t freefn)
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{
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int slot;
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KASSERT(node->pn_count <= PCTRIE_COUNT,
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("pctrie_reclaim_allnodes_int: bad count in node %p", node));
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for (slot = 0; node->pn_count != 0; slot++) {
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if (node->pn_child[slot] == NULL)
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continue;
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if (!pctrie_isleaf(node->pn_child[slot]))
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pctrie_reclaim_allnodes_int(ptree,
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node->pn_child[slot], freefn);
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node->pn_child[slot] = NULL;
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node->pn_count--;
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}
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pctrie_node_put(ptree, node, freefn);
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}
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/*
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* pctrie node zone initializer.
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*/
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int
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pctrie_zone_init(void *mem, int size __unused, int flags __unused)
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{
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struct pctrie_node *node;
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node = mem;
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memset(node->pn_child, 0, sizeof(node->pn_child));
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return (0);
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}
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size_t
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pctrie_node_size(void)
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{
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return (sizeof(struct pctrie_node));
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}
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/*
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* Inserts the key-value pair into the trie.
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* Panics if the key already exists.
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*/
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int
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pctrie_insert(struct pctrie *ptree, uint64_t *val, pctrie_alloc_t allocfn)
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{
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uint64_t index, newind;
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void **parentp;
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struct pctrie_node *node, *tmp;
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uint64_t *m;
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int slot;
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uint16_t clev;
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index = *val;
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/*
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* The owner of record for root is not really important because it
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* will never be used.
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*/
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node = pctrie_getroot(ptree);
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if (node == NULL) {
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ptree->pt_root = (uintptr_t)val | PCTRIE_ISLEAF;
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return (0);
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}
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parentp = (void **)&ptree->pt_root;
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for (;;) {
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if (pctrie_isleaf(node)) {
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m = pctrie_toval(node);
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if (*m == index)
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panic("%s: key %jx is already present",
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__func__, (uintmax_t)index);
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clev = pctrie_keydiff(*m, index);
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tmp = pctrie_node_get(ptree, allocfn,
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pctrie_trimkey(index, clev + 1), 2, clev);
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if (tmp == NULL)
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return (ENOMEM);
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*parentp = tmp;
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pctrie_addval(tmp, index, clev, val);
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pctrie_addval(tmp, *m, clev, m);
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return (0);
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} else if (pctrie_keybarr(node, index))
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break;
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slot = pctrie_slot(index, node->pn_clev);
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if (node->pn_child[slot] == NULL) {
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node->pn_count++;
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pctrie_addval(node, index, node->pn_clev, val);
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return (0);
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}
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parentp = &node->pn_child[slot];
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node = node->pn_child[slot];
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}
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/*
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* A new node is needed because the right insertion level is reached.
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* Setup the new intermediate node and add the 2 children: the
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* new object and the older edge.
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*/
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newind = node->pn_owner;
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clev = pctrie_keydiff(newind, index);
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tmp = pctrie_node_get(ptree, allocfn,
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pctrie_trimkey(index, clev + 1), 2, clev);
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if (tmp == NULL)
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return (ENOMEM);
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*parentp = tmp;
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pctrie_addval(tmp, index, clev, val);
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slot = pctrie_slot(newind, clev);
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tmp->pn_child[slot] = node;
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return (0);
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}
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/*
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* Returns the value stored at the index. If the index is not present,
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* NULL is returned.
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*/
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uint64_t *
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pctrie_lookup(struct pctrie *ptree, uint64_t index)
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{
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struct pctrie_node *node;
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uint64_t *m;
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int slot;
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node = pctrie_getroot(ptree);
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while (node != NULL) {
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if (pctrie_isleaf(node)) {
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m = pctrie_toval(node);
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if (*m == index)
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return (m);
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else
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break;
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} else if (pctrie_keybarr(node, index))
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break;
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slot = pctrie_slot(index, node->pn_clev);
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node = node->pn_child[slot];
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}
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return (NULL);
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}
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/*
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* Look up the nearest entry at a position bigger than or equal to index.
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*/
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uint64_t *
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pctrie_lookup_ge(struct pctrie *ptree, uint64_t index)
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{
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struct pctrie_node *stack[PCTRIE_LIMIT];
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uint64_t inc;
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uint64_t *m;
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struct pctrie_node *child, *node;
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#ifdef INVARIANTS
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int loops = 0;
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#endif
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int slot, tos;
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node = pctrie_getroot(ptree);
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if (node == NULL)
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return (NULL);
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else if (pctrie_isleaf(node)) {
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m = pctrie_toval(node);
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if (*m >= index)
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return (m);
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else
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return (NULL);
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}
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tos = 0;
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for (;;) {
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/*
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* If the keys differ before the current bisection node,
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* then the search key might rollback to the earliest
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* available bisection node or to the smallest key
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* in the current node (if the owner is bigger than the
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* search key).
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*/
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if (pctrie_keybarr(node, index)) {
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if (index > node->pn_owner) {
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ascend:
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KASSERT(++loops < 1000,
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("pctrie_lookup_ge: too many loops"));
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/*
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* Pop nodes from the stack until either the
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* stack is empty or a node that could have a
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* matching descendant is found.
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*/
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do {
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if (tos == 0)
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return (NULL);
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node = stack[--tos];
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} while (pctrie_slot(index,
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node->pn_clev) == (PCTRIE_COUNT - 1));
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/*
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* The following computation cannot overflow
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* because index's slot at the current level
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* is less than PCTRIE_COUNT - 1.
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*/
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index = pctrie_trimkey(index,
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node->pn_clev);
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index += PCTRIE_UNITLEVEL(node->pn_clev);
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|
} else
|
||
|
index = node->pn_owner;
|
||
|
KASSERT(!pctrie_keybarr(node, index),
|
||
|
("pctrie_lookup_ge: keybarr failed"));
|
||
|
}
|
||
|
slot = pctrie_slot(index, node->pn_clev);
|
||
|
child = node->pn_child[slot];
|
||
|
if (pctrie_isleaf(child)) {
|
||
|
m = pctrie_toval(child);
|
||
|
if (*m >= index)
|
||
|
return (m);
|
||
|
} else if (child != NULL)
|
||
|
goto descend;
|
||
|
|
||
|
/*
|
||
|
* Look for an available edge or val within the current
|
||
|
* bisection node.
|
||
|
*/
|
||
|
if (slot < (PCTRIE_COUNT - 1)) {
|
||
|
inc = PCTRIE_UNITLEVEL(node->pn_clev);
|
||
|
index = pctrie_trimkey(index, node->pn_clev);
|
||
|
do {
|
||
|
index += inc;
|
||
|
slot++;
|
||
|
child = node->pn_child[slot];
|
||
|
if (pctrie_isleaf(child)) {
|
||
|
m = pctrie_toval(child);
|
||
|
if (*m >= index)
|
||
|
return (m);
|
||
|
} else if (child != NULL)
|
||
|
goto descend;
|
||
|
} while (slot < (PCTRIE_COUNT - 1));
|
||
|
}
|
||
|
KASSERT(child == NULL || pctrie_isleaf(child),
|
||
|
("pctrie_lookup_ge: child is radix node"));
|
||
|
|
||
|
/*
|
||
|
* If a value or edge bigger than the search slot is not found
|
||
|
* in the current node, ascend to the next higher-level node.
|
||
|
*/
|
||
|
goto ascend;
|
||
|
descend:
|
||
|
KASSERT(node->pn_clev > 0,
|
||
|
("pctrie_lookup_ge: pushing leaf's parent"));
|
||
|
KASSERT(tos < PCTRIE_LIMIT,
|
||
|
("pctrie_lookup_ge: stack overflow"));
|
||
|
stack[tos++] = node;
|
||
|
node = child;
|
||
|
}
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* Look up the nearest entry at a position less than or equal to index.
|
||
|
*/
|
||
|
uint64_t *
|
||
|
pctrie_lookup_le(struct pctrie *ptree, uint64_t index)
|
||
|
{
|
||
|
struct pctrie_node *stack[PCTRIE_LIMIT];
|
||
|
uint64_t inc;
|
||
|
uint64_t *m;
|
||
|
struct pctrie_node *child, *node;
|
||
|
#ifdef INVARIANTS
|
||
|
int loops = 0;
|
||
|
#endif
|
||
|
int slot, tos;
|
||
|
|
||
|
node = pctrie_getroot(ptree);
|
||
|
if (node == NULL)
|
||
|
return (NULL);
|
||
|
else if (pctrie_isleaf(node)) {
|
||
|
m = pctrie_toval(node);
|
||
|
if (*m <= index)
|
||
|
return (m);
|
||
|
else
|
||
|
return (NULL);
|
||
|
}
|
||
|
tos = 0;
|
||
|
for (;;) {
|
||
|
/*
|
||
|
* If the keys differ before the current bisection node,
|
||
|
* then the search key might rollback to the earliest
|
||
|
* available bisection node or to the largest key
|
||
|
* in the current node (if the owner is smaller than the
|
||
|
* search key).
|
||
|
*/
|
||
|
if (pctrie_keybarr(node, index)) {
|
||
|
if (index > node->pn_owner) {
|
||
|
index = node->pn_owner + PCTRIE_COUNT *
|
||
|
PCTRIE_UNITLEVEL(node->pn_clev);
|
||
|
} else {
|
||
|
ascend:
|
||
|
KASSERT(++loops < 1000,
|
||
|
("pctrie_lookup_le: too many loops"));
|
||
|
|
||
|
/*
|
||
|
* Pop nodes from the stack until either the
|
||
|
* stack is empty or a node that could have a
|
||
|
* matching descendant is found.
|
||
|
*/
|
||
|
do {
|
||
|
if (tos == 0)
|
||
|
return (NULL);
|
||
|
node = stack[--tos];
|
||
|
} while (pctrie_slot(index,
|
||
|
node->pn_clev) == 0);
|
||
|
|
||
|
/*
|
||
|
* The following computation cannot overflow
|
||
|
* because index's slot at the current level
|
||
|
* is greater than 0.
|
||
|
*/
|
||
|
index = pctrie_trimkey(index,
|
||
|
node->pn_clev);
|
||
|
}
|
||
|
index--;
|
||
|
KASSERT(!pctrie_keybarr(node, index),
|
||
|
("pctrie_lookup_le: keybarr failed"));
|
||
|
}
|
||
|
slot = pctrie_slot(index, node->pn_clev);
|
||
|
child = node->pn_child[slot];
|
||
|
if (pctrie_isleaf(child)) {
|
||
|
m = pctrie_toval(child);
|
||
|
if (*m <= index)
|
||
|
return (m);
|
||
|
} else if (child != NULL)
|
||
|
goto descend;
|
||
|
|
||
|
/*
|
||
|
* Look for an available edge or value within the current
|
||
|
* bisection node.
|
||
|
*/
|
||
|
if (slot > 0) {
|
||
|
inc = PCTRIE_UNITLEVEL(node->pn_clev);
|
||
|
index |= inc - 1;
|
||
|
do {
|
||
|
index -= inc;
|
||
|
slot--;
|
||
|
child = node->pn_child[slot];
|
||
|
if (pctrie_isleaf(child)) {
|
||
|
m = pctrie_toval(child);
|
||
|
if (*m <= index)
|
||
|
return (m);
|
||
|
} else if (child != NULL)
|
||
|
goto descend;
|
||
|
} while (slot > 0);
|
||
|
}
|
||
|
KASSERT(child == NULL || pctrie_isleaf(child),
|
||
|
("pctrie_lookup_le: child is radix node"));
|
||
|
|
||
|
/*
|
||
|
* If a value or edge smaller than the search slot is not found
|
||
|
* in the current node, ascend to the next higher-level node.
|
||
|
*/
|
||
|
goto ascend;
|
||
|
descend:
|
||
|
KASSERT(node->pn_clev > 0,
|
||
|
("pctrie_lookup_le: pushing leaf's parent"));
|
||
|
KASSERT(tos < PCTRIE_LIMIT,
|
||
|
("pctrie_lookup_le: stack overflow"));
|
||
|
stack[tos++] = node;
|
||
|
node = child;
|
||
|
}
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* 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;
|
||
|
uint64_t *m;
|
||
|
int i, slot;
|
||
|
|
||
|
node = pctrie_getroot(ptree);
|
||
|
if (pctrie_isleaf(node)) {
|
||
|
m = pctrie_toval(node);
|
||
|
if (*m != index)
|
||
|
panic("%s: invalid key found", __func__);
|
||
|
pctrie_setroot(ptree, NULL);
|
||
|
return;
|
||
|
}
|
||
|
parent = NULL;
|
||
|
for (;;) {
|
||
|
if (node == NULL)
|
||
|
panic("pctrie_remove: impossible to locate the key");
|
||
|
slot = pctrie_slot(index, node->pn_clev);
|
||
|
if (pctrie_isleaf(node->pn_child[slot])) {
|
||
|
m = pctrie_toval(node->pn_child[slot]);
|
||
|
if (*m != index)
|
||
|
panic("%s: invalid key found", __func__);
|
||
|
node->pn_child[slot] = NULL;
|
||
|
node->pn_count--;
|
||
|
if (node->pn_count > 1)
|
||
|
break;
|
||
|
for (i = 0; i < PCTRIE_COUNT; i++)
|
||
|
if (node->pn_child[i] != NULL)
|
||
|
break;
|
||
|
KASSERT(i != PCTRIE_COUNT,
|
||
|
("%s: invalid node configuration", __func__));
|
||
|
if (parent == NULL)
|
||
|
pctrie_setroot(ptree, node->pn_child[i]);
|
||
|
else {
|
||
|
slot = pctrie_slot(index, parent->pn_clev);
|
||
|
KASSERT(parent->pn_child[slot] == node,
|
||
|
("%s: invalid child value", __func__));
|
||
|
parent->pn_child[slot] = node->pn_child[i];
|
||
|
}
|
||
|
node->pn_count--;
|
||
|
node->pn_child[i] = NULL;
|
||
|
pctrie_node_put(ptree, node, freefn);
|
||
|
break;
|
||
|
}
|
||
|
parent = node;
|
||
|
node = node->pn_child[slot];
|
||
|
}
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* 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_getroot(ptree);
|
||
|
if (root == NULL)
|
||
|
return;
|
||
|
pctrie_setroot(ptree, NULL);
|
||
|
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;
|
||
|
int i;
|
||
|
|
||
|
if (!have_addr)
|
||
|
return;
|
||
|
node = (struct pctrie_node *)addr;
|
||
|
db_printf("node %p, owner %jx, children count %u, level %u:\n",
|
||
|
(void *)node, (uintmax_t)node->pn_owner, node->pn_count,
|
||
|
node->pn_clev);
|
||
|
for (i = 0; i < PCTRIE_COUNT; i++)
|
||
|
if (node->pn_child[i] != NULL)
|
||
|
db_printf("slot: %d, val: %p, value: %p, clev: %d\n",
|
||
|
i, (void *)node->pn_child[i],
|
||
|
pctrie_isleaf(node->pn_child[i]) ?
|
||
|
pctrie_toval(node->pn_child[i]) : NULL,
|
||
|
node->pn_clev);
|
||
|
}
|
||
|
#endif /* DDB */
|