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/* Hash routine.
* Copyright (C) 1998 Kunihiro Ishiguro
*
* This file is part of GNU Zebra.
*
* GNU Zebra is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published
* by the Free Software Foundation; either version 2, or (at your
* option) any later version.
*
* GNU Zebra is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; see the file COPYING; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <zebra.h>
#include <math.h>
#include "hash.h"
#include "memory.h"
#include "linklist.h"
#include "termtable.h"
#include "vty.h"
#include "command.h"
#include "libfrr.h"
DEFINE_MTYPE(LIB, HASH, "Hash")
DEFINE_MTYPE(LIB, HASH_BACKET, "Hash Bucket")
DEFINE_MTYPE_STATIC(LIB, HASH_INDEX, "Hash Index")
pthread_mutex_t _hashes_mtx = PTHREAD_MUTEX_INITIALIZER;
static struct list *_hashes;
struct hash *hash_create_size(unsigned int size,
unsigned int (*hash_key)(void *),
int (*hash_cmp)(const void *, const void *),
const char *name)
{
struct hash *hash;
assert((size & (size - 1)) == 0);
hash = XCALLOC(MTYPE_HASH, sizeof(struct hash));
hash->index =
XCALLOC(MTYPE_HASH_INDEX, sizeof(struct hash_backet *) * size);
hash->size = size;
hash->hash_key = hash_key;
hash->hash_cmp = hash_cmp;
hash->count = 0;
hash->name = name ? XSTRDUP(MTYPE_HASH, name) : NULL;
hash->stats.empty = hash->size;
pthread_mutex_lock(&_hashes_mtx);
{
if (!_hashes)
_hashes = list_new();
listnode_add(_hashes, hash);
}
pthread_mutex_unlock(&_hashes_mtx);
return hash;
}
struct hash *hash_create(unsigned int (*hash_key)(void *),
int (*hash_cmp)(const void *, const void *),
const char *name)
{
return hash_create_size(HASH_INITIAL_SIZE, hash_key, hash_cmp, name);
}
void *hash_alloc_intern(void *arg)
{
return arg;
}
#define hash_update_ssq(hz, old, new) \
atomic_fetch_add_explicit(&hz->stats.ssq, (new + old) * (new - old), \
memory_order_relaxed);
/* Expand hash if the chain length exceeds the threshold. */
static void hash_expand(struct hash *hash)
{
unsigned int i, new_size;
struct hash_backet *hb, *hbnext, **new_index;
new_size = hash->size * 2;
if (hash->max_size && new_size > hash->max_size)
return;
new_index = XCALLOC(MTYPE_HASH_INDEX,
sizeof(struct hash_backet *) * new_size);
if (new_index == NULL)
return;
hash->stats.empty = new_size;
for (i = 0; i < hash->size; i++)
for (hb = hash->index[i]; hb; hb = hbnext) {
unsigned int h = hb->key & (new_size - 1);
hbnext = hb->next;
hb->next = new_index[h];
int oldlen = hb->next ? hb->next->len : 0;
int newlen = oldlen + 1;
if (newlen == 1)
hash->stats.empty--;
else
hb->next->len = 0;
hb->len = newlen;
hash_update_ssq(hash, oldlen, newlen);
new_index[h] = hb;
}
/* Switch to new table */
XFREE(MTYPE_HASH_INDEX, hash->index);
hash->size = new_size;
hash->index = new_index;
}
void *hash_get(struct hash *hash, void *data, void *(*alloc_func)(void *))
{
unsigned int key;
unsigned int index;
void *newdata;
struct hash_backet *backet;
if (!alloc_func && !hash->count)
return NULL;
key = (*hash->hash_key)(data);
index = key & (hash->size - 1);
for (backet = hash->index[index]; backet != NULL;
backet = backet->next) {
if (backet->key == key && (*hash->hash_cmp)(backet->data, data))
return backet->data;
}
if (alloc_func) {
newdata = (*alloc_func)(data);
if (newdata == NULL)
return NULL;
if (HASH_THRESHOLD(hash->count + 1, hash->size)) {
hash_expand(hash);
index = key & (hash->size - 1);
}
backet = XCALLOC(MTYPE_HASH_BACKET, sizeof(struct hash_backet));
backet->data = newdata;
backet->key = key;
backet->next = hash->index[index];
hash->index[index] = backet;
hash->count++;
int oldlen = backet->next ? backet->next->len : 0;
int newlen = oldlen + 1;
if (newlen == 1)
hash->stats.empty--;
else
backet->next->len = 0;
backet->len = newlen;
hash_update_ssq(hash, oldlen, newlen);
return backet->data;
}
return NULL;
}
void *hash_lookup(struct hash *hash, void *data)
{
return hash_get(hash, data, NULL);
}
unsigned int string_hash_make(const char *str)
{
unsigned int hash = 0;
while (*str)
hash = (hash * 33) ^ (unsigned int)*str++;
return hash;
}
void *hash_release(struct hash *hash, void *data)
{
void *ret;
unsigned int key;
unsigned int index;
struct hash_backet *backet;
struct hash_backet *pp;
key = (*hash->hash_key)(data);
index = key & (hash->size - 1);
for (backet = pp = hash->index[index]; backet; backet = backet->next) {
if (backet->key == key
&& (*hash->hash_cmp)(backet->data, data)) {
int oldlen = hash->index[index]->len;
int newlen = oldlen - 1;
if (backet == pp)
hash->index[index] = backet->next;
else
pp->next = backet->next;
if (hash->index[index])
hash->index[index]->len = newlen;
else
hash->stats.empty++;
hash_update_ssq(hash, oldlen, newlen);
ret = backet->data;
XFREE(MTYPE_HASH_BACKET, backet);
hash->count--;
return ret;
}
pp = backet;
}
return NULL;
}
void hash_iterate(struct hash *hash, void (*func)(struct hash_backet *, void *),
void *arg)
{
unsigned int i;
struct hash_backet *hb;
struct hash_backet *hbnext;
for (i = 0; i < hash->size; i++)
for (hb = hash->index[i]; hb; hb = hbnext) {
/* get pointer to next hash backet here, in case (*func)
* decides to delete hb by calling hash_release
*/
hbnext = hb->next;
(*func)(hb, arg);
}
}
void hash_walk(struct hash *hash, int (*func)(struct hash_backet *, void *),
void *arg)
{
unsigned int i;
struct hash_backet *hb;
struct hash_backet *hbnext;
int ret = HASHWALK_CONTINUE;
for (i = 0; i < hash->size; i++) {
for (hb = hash->index[i]; hb; hb = hbnext) {
/* get pointer to next hash backet here, in case (*func)
* decides to delete hb by calling hash_release
*/
hbnext = hb->next;
ret = (*func)(hb, arg);
if (ret == HASHWALK_ABORT)
return;
}
}
}
void hash_clean(struct hash *hash, void (*free_func)(void *))
{
unsigned int i;
struct hash_backet *hb;
struct hash_backet *next;
for (i = 0; i < hash->size; i++) {
for (hb = hash->index[i]; hb; hb = next) {
next = hb->next;
if (free_func)
(*free_func)(hb->data);
XFREE(MTYPE_HASH_BACKET, hb);
hash->count--;
}
hash->index[i] = NULL;
}
hash->stats.ssq = 0;
hash->stats.empty = hash->size;
}
static void hash_to_list_iter(struct hash_backet *hb, void *arg)
{
struct list *list = arg;
listnode_add(list, hb->data);
}
struct list *hash_to_list(struct hash *hash)
{
struct list *list = list_new();
hash_iterate(hash, hash_to_list_iter, list);
return list;
}
void hash_free(struct hash *hash)
{
pthread_mutex_lock(&_hashes_mtx);
{
if (_hashes) {
listnode_delete(_hashes, hash);
if (_hashes->count == 0) {
list_delete_and_null(&_hashes);
}
}
}
pthread_mutex_unlock(&_hashes_mtx);
if (hash->name)
XFREE(MTYPE_HASH, hash->name);
XFREE(MTYPE_HASH_INDEX, hash->index);
XFREE(MTYPE_HASH, hash);
}
/* CLI commands ------------------------------------------------------------ */
DEFUN_NOSH(show_hash_stats,
show_hash_stats_cmd,
"show debugging hashtable [statistics]",
SHOW_STR
DEBUG_STR
"Statistics about hash tables\n"
"Statistics about hash tables\n")
{
struct hash *h;
struct listnode *ln;
struct ttable *tt = ttable_new(&ttable_styles[TTSTYLE_BLANK]);
ttable_add_row(tt, "Hash table|Buckets|Entries|Empty|LF|SD|FLF|SD");
tt->style.cell.lpad = 2;
tt->style.cell.rpad = 1;
tt->style.corner = '+';
ttable_restyle(tt);
ttable_rowseps(tt, 0, BOTTOM, true, '-');
/* Summary statistics calculated are:
*
* - Load factor: This is the number of elements in the table divided
* by the number of buckets. Since this hash table implementation
* uses chaining, this value can be greater than 1.
* This number provides information on how 'full' the table is, but
* does not provide information on how evenly distributed the
* elements are.
* Notably, a load factor >= 1 does not imply that every bucket has
* an element; with a pathological hash function, all elements could
* be in a single bucket.
*
* - Full load factor: this is the number of elements in the table
* divided by the number of buckets that have some elements in them.
*
* - Std. Dev.: This is the standard deviation calculated from the
* relevant load factor. If the load factor is the mean of number of
* elements per bucket, the standard deviation measures how much any
* particular bucket is likely to deviate from the mean.
* As a rule of thumb this number should be less than 2, and ideally
* <= 1 for optimal performance. A number larger than 3 generally
* indicates a poor hash function.
*/
double lf; // load factor
double flf; // full load factor
double var; // overall variance
double fvar; // full variance
double stdv; // overall stddev
double fstdv; // full stddev
long double x2; // h->count ^ 2
long double ldc; // (long double) h->count
long double full; // h->size - h->stats.empty
long double ssq; // ssq casted to long double
pthread_mutex_lock(&_hashes_mtx);
if (!_hashes) {
pthread_mutex_unlock(&_hashes_mtx);
ttable_del(tt);
vty_out(vty, "No hash tables in use.\n");
return CMD_SUCCESS;
}
for (ALL_LIST_ELEMENTS_RO(_hashes, ln, h)) {
if (!h->name)
continue;
ssq = (long double)h->stats.ssq;
x2 = h->count * h->count;
ldc = (long double)h->count;
full = h->size - h->stats.empty;
lf = h->count / (double)h->size;
flf = full ? h->count / (double)(full) : 0;
var = ldc ? (1.0 / ldc) * (ssq - x2 / ldc) : 0;
fvar = full ? (1.0 / full) * (ssq - x2 / full) : 0;
var = (var < .0001) ? 0 : var;
fvar = (fvar < .0001) ? 0 : fvar;
stdv = sqrt(var);
fstdv = sqrt(fvar);
ttable_add_row(tt, "%s|%d|%ld|%.0f%%|%.2lf|%.2lf|%.2lf|%.2lf",
h->name, h->size, h->count,
(h->stats.empty / (double)h->size) * 100, lf,
stdv, flf, fstdv);
}
pthread_mutex_unlock(&_hashes_mtx);
/* display header */
char header[] = "Showing hash table statistics for ";
char underln[sizeof(header) + strlen(frr_protonameinst)];
memset(underln, '-', sizeof(underln));
underln[sizeof(underln) - 1] = '\0';
vty_out(vty, "%s%s\n", header, frr_protonameinst);
vty_out(vty, "%s\n", underln);
vty_out(vty, "# allocated: %d\n", _hashes->count);
vty_out(vty, "# named: %d\n\n", tt->nrows - 1);
if (tt->nrows > 1) {
ttable_colseps(tt, 0, RIGHT, true, '|');
char *table = ttable_dump(tt, "\n");
vty_out(vty, "%s\n", table);
XFREE(MTYPE_TMP, table);
} else
vty_out(vty, "No named hash tables to display.\n");
ttable_del(tt);
return CMD_SUCCESS;
}
void hash_cmd_init()
{
install_element(ENABLE_NODE, &show_hash_stats_cmd);
}
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