Merge pull request #7444 from sudhanshukumar22/bgp-clean-dampening-issue

[mirror_frr.git] / lib / hash.c

/* 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"
#include "frr_pthread.h"
#include "libfrr_trace.h"

DEFINE_MTYPE_STATIC(LIB, HASH, "Hash")
DEFINE_MTYPE_STATIC(LIB, HASH_BUCKET, "Hash Bucket")
DEFINE_MTYPE_STATIC(LIB, HASH_INDEX, "Hash Index")

static pthread_mutex_t _hashes_mtx = PTHREAD_MUTEX_INITIALIZER;
static struct list *_hashes;

struct hash *hash_create_size(unsigned int size,
                              unsigned int (*hash_key)(const void *),
                              bool (*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_bucket *) * 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;

        frr_with_mutex(&_hashes_mtx) {
                if (!_hashes)
                        _hashes = list_new();

                listnode_add(_hashes, hash);
        }

        return hash;
}

struct hash *hash_create(unsigned int (*hash_key)(const void *),
                         bool (*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;
}

/*
 * ssq = ssq + (new^2 - old^2)
 *     = ssq + ((new + old) * (new - old))
 */
#define hash_update_ssq(hz, old, new)                                          \
        do {                                                                   \
                int _adjust = (new + old) * (new - old);                       \
                if (_adjust < 0)                                               \
                        atomic_fetch_sub_explicit(&hz->stats.ssq, -_adjust,    \
                                                  memory_order_relaxed);       \
                else                                                           \
                        atomic_fetch_add_explicit(&hz->stats.ssq, _adjust,     \
                                                  memory_order_relaxed);       \
        } while (0)

/* Expand hash if the chain length exceeds the threshold. */
static void hash_expand(struct hash *hash)
{
        unsigned int i, new_size;
        struct hash_bucket *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_bucket *) * new_size);

        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 *))
{
        frrtrace(2, frr_libfrr, hash_get, hash, data);

        unsigned int key;
        unsigned int index;
        void *newdata;
        struct hash_bucket *bucket;

        if (!alloc_func && !hash->count)
                return NULL;

        key = (*hash->hash_key)(data);
        index = key & (hash->size - 1);

        for (bucket = hash->index[index]; bucket != NULL;
             bucket = bucket->next) {
                if (bucket->key == key && (*hash->hash_cmp)(bucket->data, data))
                        return bucket->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);
                }

                bucket = XCALLOC(MTYPE_HASH_BUCKET, sizeof(struct hash_bucket));
                bucket->data = newdata;
                bucket->key = key;
                bucket->next = hash->index[index];
                hash->index[index] = bucket;
                hash->count++;

                frrtrace(3, frr_libfrr, hash_insert, hash, data, key);

                int oldlen = bucket->next ? bucket->next->len : 0;
                int newlen = oldlen + 1;

                if (newlen == 1)
                        hash->stats.empty--;
                else
                        bucket->next->len = 0;

                bucket->len = newlen;

                hash_update_ssq(hash, oldlen, newlen);

                return bucket->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 = NULL;
        unsigned int key;
        unsigned int index;
        struct hash_bucket *bucket;
        struct hash_bucket *pp;

        key = (*hash->hash_key)(data);
        index = key & (hash->size - 1);

        for (bucket = pp = hash->index[index]; bucket; bucket = bucket->next) {
                if (bucket->key == key
                    && (*hash->hash_cmp)(bucket->data, data)) {
                        int oldlen = hash->index[index]->len;
                        int newlen = oldlen - 1;

                        if (bucket == pp)
                                hash->index[index] = bucket->next;
                        else
                                pp->next = bucket->next;

                        if (hash->index[index])
                                hash->index[index]->len = newlen;
                        else
                                hash->stats.empty++;

                        hash_update_ssq(hash, oldlen, newlen);

                        ret = bucket->data;
                        XFREE(MTYPE_HASH_BUCKET, bucket);
                        hash->count--;
                        break;
                }
                pp = bucket;
        }

        frrtrace(3, frr_libfrr, hash_release, hash, data, ret);

        return ret;
}

void hash_iterate(struct hash *hash, void (*func)(struct hash_bucket *, void *),
                  void *arg)
{
        unsigned int i;
        struct hash_bucket *hb;
        struct hash_bucket *hbnext;

        for (i = 0; i < hash->size; i++)
                for (hb = hash->index[i]; hb; hb = hbnext) {
                        /* get pointer to next hash bucket 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_bucket *, void *),
               void *arg)
{
        unsigned int i;
        struct hash_bucket *hb;
        struct hash_bucket *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 bucket 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_bucket *hb;
        struct hash_bucket *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_BUCKET, hb);
                        hash->count--;
                }
                hash->index[i] = NULL;
        }

        hash->stats.ssq = 0;
        hash->stats.empty = hash->size;
}

static void hash_to_list_iter(struct hash_bucket *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)
{
        frr_with_mutex(&_hashes_mtx) {
                if (_hashes) {
                        listnode_delete(_hashes, hash);
                        if (_hashes->count == 0) {
                                list_delete(&_hashes);
                        }
                }
        }

        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(void)
{
        install_element(ENABLE_NODE, &show_hash_stats_cmd);
}