thodg/got/lib/object_idcache.c

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• Hash : bb7182a5
  Author :
  Date : 2018-09-16T16:12:58
  

  speed up object id cache by using multiple lists

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• lib/object_idcache.c

• /*
   * Copyright (c) 2018 Stefan Sperling <stsp@openbsd.org>
   *
   * Permission to use, copy, modify, and distribute this software for any
   * purpose with or without fee is hereby granted, provided that the above
   * copyright notice and this permission notice appear in all copies.
   *
   * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
   * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
   * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
   * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
   * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
   * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
   * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
   */
  
  #include <sys/queue.h>
  
  #include <stdlib.h>
  #include <string.h>
  #include <sha1.h>
  #include <stdio.h>
  #include <zlib.h>
  #include <limits.h>
  #include <time.h>
  
  #include "got_object.h"
  #include "got_error.h"
  
  #include "got_lib_delta.h"
  #include "got_lib_inflate.h"
  #include "got_lib_object.h"
  #include "got_lib_object_idcache.h"
  
  #ifndef nitems
  #define nitems(_a) (sizeof(_a) / sizeof((_a)[0]))
  #endif
  
  struct got_object_idcache_element {
  	TAILQ_ENTRY(got_object_idcache_element) entry;
  	struct got_object_id id;
  	void *data;	/* API user data */
  };
  
  TAILQ_HEAD(got_object_idcache_head, got_object_idcache_element);
  
  struct got_object_idcache {
  	/*
  	 * The cache is implemented as a collection of 256 lists.
  	 * The value of the first byte of an object ID determines
  	 * which of these lists an object ID is stored in.
  	 */
  	struct got_object_idcache_head entries[0xff + 1];
  	int nelem[0xff + 1];
  	int totelem;
  	int maxelem;
  };
  
  struct got_object_idcache *
  got_object_idcache_alloc(int maxelem)
  {
  	struct got_object_idcache *cache;
  	int i;
  
  	cache = calloc(1, sizeof(*cache));
  	if (cache == NULL)
  		return NULL;
  
  	for (i = 0; i < nitems(cache->entries); i++)
  		TAILQ_INIT(&cache->entries[i]);
  	cache->maxelem = maxelem;
  	return cache;
  }
  
  void
  got_object_idcache_free(struct got_object_idcache *cache)
  {
  	struct got_object_idcache_element *entry;
  	int i;
  
  	for (i = 0; i < nitems(cache->entries); i++) {
  		while (!TAILQ_EMPTY(&cache->entries[i])) {
  			entry = TAILQ_FIRST(&cache->entries[i]);
  			TAILQ_REMOVE(&cache->entries[i], entry, entry);
  			/* User data should be freed by caller. */
  			free(entry);
  		}
  	}
  	free(cache);
  }
  
  const struct got_error *
  got_object_idcache_add(struct got_object_idcache *cache,
      struct got_object_id *id, void *data)
  {
  	struct got_object_idcache_element *entry;
  	uint8_t i = id->sha1[0];
  
  	if (cache->totelem >= cache->maxelem)
  		return got_error(GOT_ERR_NO_SPACE);
  
  	entry = calloc(1, sizeof(*entry));
  	if (entry == NULL)
  		return got_error_from_errno();
  
  	memcpy(&entry->id, id, sizeof(entry->id));
  	entry->data = data;
  
  	TAILQ_INSERT_HEAD(&cache->entries[i], entry, entry);
  	cache->nelem[i]++;
  	cache->totelem++;
  	return NULL;
  }
  
  void *
  got_object_idcache_get(struct got_object_idcache *cache, struct got_object_id *id)
  {
  	struct got_object_idcache_element *entry;
  	uint8_t i = id->sha1[0];
  
  	TAILQ_FOREACH(entry, &cache->entries[i], entry) {
  		if (memcmp(&entry->id.sha1, id->sha1, SHA1_DIGEST_LENGTH) != 0)
  			continue;
  		if (entry != TAILQ_FIRST(&cache->entries[i])) {
  			TAILQ_REMOVE(&cache->entries[i], entry, entry);
  			TAILQ_INSERT_HEAD(&cache->entries[i], entry, entry);
  		}
  		return entry->data;
  	}
  
  	return NULL;
  }
  
  const struct got_error *
  got_object_idcache_remove_least_used(void **data, struct got_object_idcache *cache)
  {
  	struct got_object_idcache_element *entry;
  	int i, idx = 0, maxelem = cache->nelem[0];
  
  	if (data)
  		*data = NULL;
  
  	if (cache->totelem == 0)
  		return got_error(GOT_ERR_NO_OBJ);
  
  	/* Remove least used element from longest list. */
  	for (i = 0; i < nitems(cache->entries); i++) {
  		if (maxelem < cache->nelem[i]) {
  			idx = i;
  			maxelem = cache->nelem[i];
  		}
  	}
  	entry = TAILQ_LAST(&cache->entries[idx], got_object_idcache_head);
  	TAILQ_REMOVE(&cache->entries[idx], entry, entry);
  	if (data)
  		*data = entry->data;
  	free(entry);
  	cache->nelem[idx]--;
  	cache->totelem--;
  	return NULL;
  }
  
  int
  got_object_idcache_contains(struct got_object_idcache *cache,
      struct got_object_id *id)
  {
  	struct got_object_idcache_element *entry;
  	uint8_t i = id->sha1[0];
  
  	TAILQ_FOREACH(entry, &cache->entries[i], entry) {
  		if (memcmp(&entry->id.sha1, id->sha1, SHA1_DIGEST_LENGTH) == 0)
  			return 1;
  	}
  
  	return 0;
  }
  
  void got_object_idcache_for_each(struct got_object_idcache *cache,
      void (*cb)(struct got_object_id *, void *, void *), void *arg)
  {
  	struct got_object_idcache_element *entry;
  	int i;
  
  	for (i = 0; i < nitems(cache->entries); i++) {
  		TAILQ_FOREACH(entry, &cache->entries[i], entry)
  			cb(&entry->id, entry->data, arg);
  	}
  }
  
  int
  got_object_idcache_num_elements(struct got_object_idcache *cache)
  {
  	return cache->totelem;
  }
  

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