702 lines
19 KiB
C
702 lines
19 KiB
C
/*-
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* SPDX-License-Identifier: BSD-2-Clause
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*
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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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#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/libkern.h>
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#include <sys/pctrie.h>
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#include <sys/proc.h> /* smr.h depends on struct thread. */
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#include <sys/smr.h>
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#include <sys/smr_types.h>
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#ifdef DDB
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#include <ddb/ddb.h>
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#endif
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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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#if PCTRIE_WIDTH == 3
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typedef uint8_t pn_popmap_t;
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#elif PCTRIE_WIDTH == 4
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typedef uint16_t pn_popmap_t;
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#elif PCTRIE_WIDTH == 5
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typedef uint32_t pn_popmap_t;
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#else
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#error Unsupported width
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#endif
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_Static_assert(sizeof(pn_popmap_t) <= sizeof(int),
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"pn_popmap_t too wide");
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/* Set of all flag bits stored in node pointers. */
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#define PCTRIE_FLAGS (PCTRIE_ISLEAF)
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#define PCTRIE_PAD PCTRIE_FLAGS
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struct pctrie_node;
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typedef SMR_POINTER(struct pctrie_node *) smr_pctnode_t;
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struct pctrie_node {
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uint64_t pn_owner; /* Owner of record. */
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pn_popmap_t pn_popmap; /* Valid children. */
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uint8_t pn_clev; /* Level * WIDTH. */
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smr_pctnode_t pn_child[PCTRIE_COUNT]; /* Child nodes. */
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};
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enum pctrie_access { PCTRIE_SMR, PCTRIE_LOCKED, PCTRIE_UNSERIALIZED };
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static __inline void pctrie_node_store(smr_pctnode_t *p, void *val,
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enum pctrie_access access);
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/*
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* Map index to an array position for the children of node,
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*/
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static __inline int
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pctrie_slot(struct pctrie_node *node, uint64_t index)
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{
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return ((index >> node->pn_clev) & PCTRIE_MASK);
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}
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/*
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* Returns true if index does not belong to the specified node. Otherwise,
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* sets slot value, and returns false.
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*/
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static __inline bool
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pctrie_keybarr(struct pctrie_node *node, uint64_t index, int *slot)
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{
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index = (index - node->pn_owner) >> node->pn_clev;
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if (index >= PCTRIE_COUNT)
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return (true);
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*slot = index;
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return (false);
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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 struct pctrie_node *
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pctrie_node_get(struct pctrie *ptree, pctrie_alloc_t allocfn, uint64_t index,
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uint64_t newind)
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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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/*
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* We want to clear the last child pointer after the final section
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* has exited so lookup can not return false negatives. It is done
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* here because it will be cache-cold in the dtor callback.
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*/
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if (node->pn_popmap != 0) {
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pctrie_node_store(&node->pn_child[ffs(node->pn_popmap) - 1],
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PCTRIE_NULL, PCTRIE_UNSERIALIZED);
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node->pn_popmap = 0;
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}
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/*
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* From the highest-order bit where the indexes differ,
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* compute the highest level in the trie where they differ. Then,
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* compute the least index of this subtrie.
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*/
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KASSERT(index != newind, ("%s: passing the same key value %jx",
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__func__, (uintmax_t)index));
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_Static_assert(sizeof(long long) >= sizeof(uint64_t),
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"uint64 too wide");
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_Static_assert(sizeof(uint64_t) * NBBY <=
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(1 << (sizeof(node->pn_clev) * NBBY)), "pn_clev too narrow");
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node->pn_clev = rounddown(flsll(index ^ newind) - 1, PCTRIE_WIDTH);
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node->pn_owner = PCTRIE_COUNT;
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node->pn_owner = index & -(node->pn_owner << node->pn_clev);
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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(powerof2(node->pn_popmap),
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("pctrie_node_put: node %p has too many children %04x", node,
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node->pn_popmap));
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for (slot = 0; slot < PCTRIE_COUNT; slot++) {
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if ((node->pn_popmap & (1 << slot)) != 0)
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continue;
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KASSERT(smr_unserialized_load(&node->pn_child[slot], true) ==
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PCTRIE_NULL,
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("pctrie_node_put: node %p has a child", node));
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}
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#endif
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freefn(ptree, node);
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}
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/*
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* Fetch a node pointer from a slot.
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*/
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static __inline struct pctrie_node *
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pctrie_node_load(smr_pctnode_t *p, smr_t smr, enum pctrie_access access)
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{
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switch (access) {
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case PCTRIE_UNSERIALIZED:
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return (smr_unserialized_load(p, true));
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case PCTRIE_LOCKED:
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return (smr_serialized_load(p, true));
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case PCTRIE_SMR:
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return (smr_entered_load(p, smr));
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}
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__assert_unreachable();
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}
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static __inline void
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pctrie_node_store(smr_pctnode_t *p, void *v, enum pctrie_access access)
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{
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switch (access) {
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case PCTRIE_UNSERIALIZED:
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smr_unserialized_store(p, v, true);
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break;
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case PCTRIE_LOCKED:
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smr_serialized_store(p, v, true);
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break;
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case PCTRIE_SMR:
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panic("%s: Not supported in SMR section.", __func__);
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break;
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default:
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__assert_unreachable();
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break;
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}
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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_root_load(struct pctrie *ptree, smr_t smr, enum pctrie_access access)
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{
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return (pctrie_node_load((smr_pctnode_t *)&ptree->pt_root, smr, access));
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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_root_store(struct pctrie *ptree, struct pctrie_node *node,
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enum pctrie_access access)
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{
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pctrie_node_store((smr_pctnode_t *)&ptree->pt_root, node, access);
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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 bool
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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 val with leaf bit set.
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*/
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static __inline void *
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pctrie_toleaf(uint64_t *val)
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{
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return ((void *)((uintptr_t)val | PCTRIE_ISLEAF));
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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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* Make 'child' a child of 'node'.
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*/
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static __inline void
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pctrie_addnode(struct pctrie_node *node, uint64_t index,
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struct pctrie_node *child, enum pctrie_access access)
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{
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int slot;
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slot = pctrie_slot(node, index);
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pctrie_node_store(&node->pn_child[slot], child, access);
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node->pn_popmap ^= 1 << slot;
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KASSERT((node->pn_popmap & (1 << slot)) != 0,
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("%s: bad popmap slot %d in node %p", __func__, slot, node));
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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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struct pctrie_node *child;
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int slot;
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while (node->pn_popmap != 0) {
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slot = ffs(node->pn_popmap) - 1;
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child = pctrie_node_load(&node->pn_child[slot], NULL,
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PCTRIE_UNSERIALIZED);
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KASSERT(child != PCTRIE_NULL,
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("%s: bad popmap slot %d in node %p",
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__func__, slot, node));
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if (!pctrie_isleaf(child))
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pctrie_reclaim_allnodes_int(ptree, child, freefn);
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node->pn_popmap ^= 1 << slot;
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pctrie_node_store(&node->pn_child[slot], PCTRIE_NULL,
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PCTRIE_UNSERIALIZED);
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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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node->pn_popmap = 0;
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for (int i = 0; i < nitems(node->pn_child); i++)
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pctrie_node_store(&node->pn_child[i], PCTRIE_NULL,
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PCTRIE_UNSERIALIZED);
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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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struct pctrie_node *leaf, *node, *parent;
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smr_pctnode_t *parentp;
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int slot;
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index = *val;
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leaf = pctrie_toleaf(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_root_load(ptree, NULL, PCTRIE_LOCKED);
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parent = NULL;
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for (;;) {
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if (pctrie_isleaf(node)) {
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if (node == PCTRIE_NULL) {
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if (parent == NULL)
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ptree->pt_root = leaf;
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else
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pctrie_addnode(parent, index, leaf,
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PCTRIE_LOCKED);
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return (0);
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}
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newind = *pctrie_toval(node);
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if (newind == index)
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panic("%s: key %jx is already present",
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__func__, (uintmax_t)index);
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break;
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}
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if (pctrie_keybarr(node, index, &slot)) {
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newind = node->pn_owner;
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break;
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}
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parent = node;
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node = pctrie_node_load(&node->pn_child[slot], NULL,
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PCTRIE_LOCKED);
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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 or object.
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*/
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parentp = (parent != NULL) ? &parent->pn_child[slot]:
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(smr_pctnode_t *)&ptree->pt_root;
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parent = pctrie_node_get(ptree, allocfn, index, newind);
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if (parent == NULL)
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return (ENOMEM);
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/* These writes are not yet visible due to ordering. */
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pctrie_addnode(parent, index, leaf, PCTRIE_UNSERIALIZED);
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pctrie_addnode(parent, newind, node, PCTRIE_UNSERIALIZED);
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/* Synchronize to make the above visible. */
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pctrie_node_store(parentp, parent, PCTRIE_LOCKED);
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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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static __always_inline uint64_t *
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_pctrie_lookup(struct pctrie *ptree, uint64_t index, smr_t smr,
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enum pctrie_access access)
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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_root_load(ptree, smr, access);
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for (;;) {
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if (pctrie_isleaf(node)) {
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if ((m = pctrie_toval(node)) != NULL && *m == index)
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return (m);
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break;
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}
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if (pctrie_keybarr(node, index, &slot))
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break;
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node = pctrie_node_load(&node->pn_child[slot], smr, access);
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}
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return (NULL);
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}
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/*
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* Returns the value stored at the index, assuming access is externally
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* synchronized by a lock.
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*
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* If the index is not present, 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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return (_pctrie_lookup(ptree, index, NULL, PCTRIE_LOCKED));
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}
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/*
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* Returns the value stored at the index without requiring an external lock.
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*
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* If the index is not present, NULL is returned.
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*/
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uint64_t *
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pctrie_lookup_unlocked(struct pctrie *ptree, uint64_t index, smr_t smr)
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{
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uint64_t *res;
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smr_enter(smr);
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res = _pctrie_lookup(ptree, index, smr, PCTRIE_SMR);
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smr_exit(smr);
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return (res);
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}
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/*
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* Returns the value with the least index that is greater than or equal to the
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* specified index, or NULL if there are no such values.
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*
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* Requires that access be externally synchronized by a lock.
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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 *node, *succ;
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uint64_t *m;
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int slot;
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/*
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* Descend the trie as if performing an ordinary lookup for the
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* specified value. However, unlike an ordinary lookup, as we descend
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* the trie, we use "succ" to remember the last branching-off point,
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* that is, the interior node under which the least value that is both
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* outside our current path down the trie and greater than the specified
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* index resides. (The node's popmap makes it fast and easy to
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* recognize a branching-off point.) If our ordinary lookup fails to
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* yield a value that is greater than or equal to the specified index,
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* then we will exit this loop and perform a lookup starting from
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* "succ". If "succ" is not NULL, then that lookup is guaranteed to
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* succeed.
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*/
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node = pctrie_root_load(ptree, NULL, PCTRIE_LOCKED);
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succ = NULL;
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for (;;) {
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if (pctrie_isleaf(node)) {
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if ((m = pctrie_toval(node)) != NULL && *m >= index)
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return (m);
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break;
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}
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if (pctrie_keybarr(node, index, &slot)) {
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/*
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* If all values in this subtree are > index, then the
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* least value in this subtree is the answer.
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*/
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if (node->pn_owner > index)
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succ = node;
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break;
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}
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/*
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* Just in case the next search step leads to a subtree of all
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|
* 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(succ, index) + 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;
|
|
for (;;) {
|
|
if (pctrie_isleaf(node)) {
|
|
if ((m = pctrie_toval(node)) != NULL && *m <= index)
|
|
return (m);
|
|
break;
|
|
}
|
|
if (pctrie_keybarr(node, index, &slot)) {
|
|
if (node->pn_owner < index)
|
|
pred = node;
|
|
break;
|
|
}
|
|
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(pred, index);
|
|
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 *child, *node, *parent;
|
|
uint64_t *m;
|
|
int slot;
|
|
|
|
node = NULL;
|
|
child = pctrie_root_load(ptree, NULL, PCTRIE_LOCKED);
|
|
for (;;) {
|
|
if (pctrie_isleaf(child))
|
|
break;
|
|
parent = node;
|
|
node = child;
|
|
slot = pctrie_slot(node, index);
|
|
child = pctrie_node_load(&node->pn_child[slot], NULL,
|
|
PCTRIE_LOCKED);
|
|
}
|
|
if ((m = pctrie_toval(child)) == NULL || *m != index)
|
|
panic("%s: key not found", __func__);
|
|
if (node == NULL) {
|
|
pctrie_root_store(ptree, PCTRIE_NULL, PCTRIE_LOCKED);
|
|
return;
|
|
}
|
|
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], PCTRIE_NULL, PCTRIE_LOCKED);
|
|
if (!powerof2(node->pn_popmap))
|
|
return;
|
|
KASSERT(node->pn_popmap != 0, ("%s: bad popmap all zeroes", __func__));
|
|
slot = ffs(node->pn_popmap) - 1;
|
|
child = pctrie_node_load(&node->pn_child[slot], NULL, PCTRIE_LOCKED);
|
|
KASSERT(child != PCTRIE_NULL,
|
|
("%s: bad popmap slot %d in node %p", __func__, slot, node));
|
|
if (parent == NULL)
|
|
pctrie_root_store(ptree, child, PCTRIE_LOCKED);
|
|
else {
|
|
slot = pctrie_slot(parent, index);
|
|
KASSERT(node ==
|
|
pctrie_node_load(&parent->pn_child[slot], NULL,
|
|
PCTRIE_LOCKED), ("%s: invalid child value", __func__));
|
|
pctrie_node_store(&parent->pn_child[slot], child,
|
|
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);
|
|
}
|
|
|
|
/*
|
|
* 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 == PCTRIE_NULL)
|
|
return;
|
|
pctrie_root_store(ptree, PCTRIE_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 / PCTRIE_WIDTH);
|
|
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 / PCTRIE_WIDTH);
|
|
}
|
|
}
|
|
#endif /* DDB */
|