/*-
* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
*
* Copyright (c) 2013 EMC Corp.
* Copyright (c) 2011 Jeffrey Roberson <jeff@freebsd.org>
* Copyright (c) 2008 Mayur Shardul <mayur.shardul@gmail.com>
* 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 <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "opt_ddb.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/pctrie.h>
#ifdef DDB
#include <ddb/ddb.h>
#endif
#define PCTRIE_MASK (PCTRIE_COUNT - 1)
#define PCTRIE_LIMIT (howmany(sizeof(uint64_t) * NBBY, PCTRIE_WIDTH) - 1)
/* 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 {
uint64_t pn_owner; /* Owner of record. */
uint16_t pn_count; /* Valid children. */
uint16_t pn_clev; /* Current level. */
void *pn_child[PCTRIE_COUNT]; /* Child nodes. */
};
/*
* Allocate a node. Pre-allocation should ensure that the request
* will always be satisfied.
*/
static __inline struct pctrie_node *
pctrie_node_get(struct pctrie *ptree, pctrie_alloc_t allocfn, uint64_t owner,
uint16_t count, uint16_t clevel)
{
struct pctrie_node *node;
node = allocfn(ptree);
if (node == NULL)
return (NULL);
node->pn_owner = owner;
node->pn_count = count;
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(node->pn_count == 0,
("pctrie_node_put: node %p has %d children", node,
node->pn_count));
for (slot = 0; slot < PCTRIE_COUNT; slot++)
KASSERT(node->pn_child[slot] == NULL,
("pctrie_node_put: node %p has a child", node));
#endif
freefn(ptree, node);
}
/*
* 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);
}
/* Trims the key after the specified level. */
static __inline uint64_t
pctrie_trimkey(uint64_t index, uint16_t level)
{
uint64_t ret;
ret = index;
if (level > 0) {
ret >>= level * PCTRIE_WIDTH;
ret <<= level * PCTRIE_WIDTH;
}
return (ret);
}
/*
* Get the root node for a tree.
*/
static __inline struct pctrie_node *
pctrie_getroot(struct pctrie *ptree)
{
return ((struct pctrie_node *)ptree->pt_root);
}
/*
* Set the root node for a tree.
*/
static __inline void
pctrie_setroot(struct pctrie *ptree, struct pctrie_node *node)
{
ptree->pt_root = (uintptr_t)node;
}
/*
* 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 the associated val extracted from node.
*/
static __inline uint64_t *
pctrie_toval(struct pctrie_node *node)
{
return ((uint64_t *)((uintptr_t)node & ~PCTRIE_FLAGS));
}
/*
* Adds the val as a child of the provided node.
*/
static __inline void
pctrie_addval(struct pctrie_node *node, uint64_t index, uint16_t clev,
uint64_t *val)
{
int slot;
slot = pctrie_slot(index, clev);
node->pn_child[slot] = (void *)((uintptr_t)val | PCTRIE_ISLEAF);
}
/*
* Returns the slot where two keys differ.
* It cannot accept 2 equal keys.
*/
static __inline uint16_t
pctrie_keydiff(uint64_t index1, uint64_t index2)
{
uint16_t clev;
KASSERT(index1 != index2, ("%s: passing the same key value %jx",
__func__, (uintmax_t)index1));
index1 ^= index2;
for (clev = PCTRIE_LIMIT;; clev--)
if (pctrie_slot(index1, clev) != 0)
return (clev);
}
/*
* 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)
{
int slot;
KASSERT(node->pn_count <= PCTRIE_COUNT,
("pctrie_reclaim_allnodes_int: bad count in node %p", node));
for (slot = 0; node->pn_count != 0; slot++) {
if (node->pn_child[slot] == NULL)
continue;
if (!pctrie_isleaf(node->pn_child[slot]))
pctrie_reclaim_allnodes_int(ptree,
node->pn_child[slot], freefn);
node->pn_child[slot] = NULL;
node->pn_count--;
}
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;
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;
void **parentp;
struct pctrie_node *node, *tmp;
uint64_t *m;
int slot;
uint16_t clev;
index = *val;
/*
* The owner of record for root is not really important because it
* will never be used.
*/
node = pctrie_getroot(ptree);
if (node == NULL) {
ptree->pt_root = (uintptr_t)val | PCTRIE_ISLEAF;
return (0);
}
parentp = (void **)&ptree->pt_root;
for (;;) {
if (pctrie_isleaf(node)) {
m = pctrie_toval(node);
if (*m == index)
panic("%s: key %jx is already present",
__func__, (uintmax_t)index);
clev = pctrie_keydiff(*m, index);
tmp = pctrie_node_get(ptree, allocfn,
pctrie_trimkey(index, clev + 1), 2, clev);
if (tmp == NULL)
return (ENOMEM);
*parentp = tmp;
pctrie_addval(tmp, index, clev, val);
pctrie_addval(tmp, *m, clev, m);
return (0);
} else if (pctrie_keybarr(node, index))
break;
slot = pctrie_slot(index, node->pn_clev);
if (node->pn_child[slot] == NULL) {
node->pn_count++;
pctrie_addval(node, index, node->pn_clev, val);
return (0);
}
parentp = &node->pn_child[slot];
node = node->pn_child[slot];
}
/*
* 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.
*/
newind = node->pn_owner;
clev = pctrie_keydiff(newind, index);
tmp = pctrie_node_get(ptree, allocfn,
pctrie_trimkey(index, clev + 1), 2, clev);
if (tmp == NULL)
return (ENOMEM);
*parentp = tmp;
pctrie_addval(tmp, index, clev, val);
slot = pctrie_slot(newind, clev);
tmp->pn_child[slot] = node;
return (0);
}
/*
* Returns the value stored at the index. If the index is not present,
* NULL is returned.
*/
uint64_t *
pctrie_lookup(struct pctrie *ptree, uint64_t index)
{
struct pctrie_node *node;
uint64_t *m;
int slot;
node = pctrie_getroot(ptree);
while (node != NULL) {
if (pctrie_isleaf(node)) {
m = pctrie_toval(node);
if (*m == index)
return (m);
else
break;
} else if (pctrie_keybarr(node, index))
break;
slot = pctrie_slot(index, node->pn_clev);
node = node->pn_child[slot];
}
return (NULL);
}
/*
* Look up the nearest entry at a position bigger than or equal to index.
*/
uint64_t *
pctrie_lookup_ge(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
unsigned tos;
int slot;
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 smallest key
* in the current node (if the owner is bigger than the
* search key).
*/
if (pctrie_keybarr(node, index)) {
if (index > node->pn_owner) {
ascend:
KASSERT(++loops < 1000,
("pctrie_lookup_ge: 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) == (PCTRIE_COUNT - 1));
/*
* The following computation cannot overflow
* because index's slot at the current level
* is less than PCTRIE_COUNT - 1.
*/
index = pctrie_trimkey(index,
node->pn_clev);
index += PCTRIE_UNITLEVEL(node->pn_clev);
} 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
unsigned tos;
int slot;
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 */
