src/cache.c

   1 /*
   2  * Copyright (C) the libgit2 contributors. All rights reserved.
   3  *
   4  * This file is part of libgit2, distributed under the GNU GPL v2 with
   5  * a Linking Exception. For full terms see the included COPYING file.
   6  */
   7
   8 #include "common.h"
   9 #include "repository.h"
  10 #include "commit.h"
  11 #include "thread-utils.h"
  12 #include "util.h"
  13 #include "cache.h"
  14 #include "odb.h"
  15 #include "object.h"
  16 #include "git2/oid.h"
  17
  18 bool git_cache__enabled = true;
  19 ssize_t git_cache__max_storage = (256 * 1024 * 1024);
  20 git_atomic_ssize git_cache__current_storage = {0};
  21
  22 static size_t git_cache__max_object_size[8] = {
  23         0,     /* GIT_OBJ__EXT1 */
  24         4096,  /* GIT_OBJ_COMMIT */
  25         4096,  /* GIT_OBJ_TREE */
  26         0,     /* GIT_OBJ_BLOB */
  27         4096,  /* GIT_OBJ_TAG */
  28         0,     /* GIT_OBJ__EXT2 */
  29         0,     /* GIT_OBJ_OFS_DELTA */
  30         0      /* GIT_OBJ_REF_DELTA */
  31 };
  32
  33 int git_cache_set_max_object_size(git_otype type, size_t size)
  34 {
  35         if (type < 0 || (size_t)type >= ARRAY_SIZE(git_cache__max_object_size)) {
  36                 giterr_set(GITERR_INVALID, "type out of range");
  37                 return -1;
  38         }
  39
  40         git_cache__max_object_size[type] = size;
  41         return 0;
  42 }
  43
  44 void git_cache_dump_stats(git_cache *cache)
  45 {
  46         git_cached_obj *object;
  47
  48         if (git_cache_size(cache) == 0)
  49                 return;
  50
  51         printf("Cache %p: %"PRIuZ" items cached, %"PRIdZ" bytes\n",
  52                 cache, git_cache_size(cache), cache->used_memory);
  53
  54         git_oidmap_foreach_value(cache->map, object, {
  55                 char oid_str[9];
  56                 printf(" %s%c %s (%"PRIuZ")\n",
  57                         git_object_type2string(object->type),
  58                         object->flags == GIT_CACHE_STORE_PARSED ? '*' : ' ',
  59                         git_oid_tostr(oid_str, sizeof(oid_str), &object->oid),
  60                         object->size
  61                 );
  62         });
  63 }
  64
  65 int git_cache_init(git_cache *cache)
  66 {
  67         memset(cache, 0, sizeof(*cache));
  68         cache->map = git_oidmap_alloc();
  69         GITERR_CHECK_ALLOC(cache->map);
  70         if (git_rwlock_init(&cache->lock)) {
  71                 giterr_set(GITERR_OS, "failed to initialize cache rwlock");
  72                 return -1;
  73         }
  74         return 0;
  75 }
  76
  77 /* called with lock */
  78 static void clear_cache(git_cache *cache)
  79 {
  80         git_cached_obj *evict = NULL;
  81
  82         if (git_cache_size(cache) == 0)
  83                 return;
  84
  85         git_oidmap_foreach_value(cache->map, evict, {
  86                 git_cached_obj_decref(evict);
  87         });
  88
  89         git_oidmap_clear(cache->map);
  90         git_atomic_ssize_add(&git_cache__current_storage, -cache->used_memory);
  91         cache->used_memory = 0;
  92 }
  93
  94 void git_cache_clear(git_cache *cache)
  95 {
  96         if (git_rwlock_wrlock(&cache->lock) < 0)
  97                 return;
  98
  99         clear_cache(cache);
 100
 101         git_rwlock_wrunlock(&cache->lock);
 102 }
 103
 104 void git_cache_free(git_cache *cache)
 105 {
 106         git_cache_clear(cache);
 107         git_oidmap_free(cache->map);
 108         git_rwlock_free(&cache->lock);
 109         git__memzero(cache, sizeof(*cache));
 110 }
 111
 112 /* Called with lock */
 113 static void cache_evict_entries(git_cache *cache)
 114 {
 115         uint32_t seed = rand();
 116         size_t evict_count = 8;
 117         ssize_t evicted_memory = 0;
 118
 119         /* do not infinite loop if there's not enough entries to evict  */
 120         if (evict_count > git_cache_size(cache)) {
 121                 clear_cache(cache);
 122                 return;
 123         }
 124
 125         while (evict_count > 0) {
 126                 khiter_t pos = seed++ % git_oidmap_end(cache->map);
 127
 128                 if (git_oidmap_has_data(cache->map, pos)) {
 129                         git_cached_obj *evict = git_oidmap_value_at(cache->map, pos);
 130
 131                         evict_count--;
 132                         evicted_memory += evict->size;
 133                         git_cached_obj_decref(evict);
 134
 135                         git_oidmap_delete_at(cache->map, pos);
 136                 }
 137         }
 138
 139         cache->used_memory -= evicted_memory;
 140         git_atomic_ssize_add(&git_cache__current_storage, -evicted_memory);
 141 }
 142
 143 static bool cache_should_store(git_otype object_type, size_t object_size)
 144 {
 145         size_t max_size = git_cache__max_object_size[object_type];
 146         return git_cache__enabled && object_size < max_size;
 147 }
 148
 149 static void *cache_get(git_cache *cache, const git_oid *oid, unsigned int flags)
 150 {
 151         khiter_t pos;
 152         git_cached_obj *entry = NULL;
 153
 154         if (!git_cache__enabled || git_rwlock_rdlock(&cache->lock) < 0)
 155                 return NULL;
 156
 157         pos = git_oidmap_lookup_index(cache->map, oid);
 158         if (git_oidmap_valid_index(cache->map, pos)) {
 159                 entry = git_oidmap_value_at(cache->map, pos);
 160
 161                 if (flags && entry->flags != flags) {
 162                         entry = NULL;
 163                 } else {
 164                         git_cached_obj_incref(entry);
 165                 }
 166         }
 167
 168         git_rwlock_rdunlock(&cache->lock);
 169
 170         return entry;
 171 }
 172
 173 static void *cache_store(git_cache *cache, git_cached_obj *entry)
 174 {
 175         khiter_t pos;
 176
 177         git_cached_obj_incref(entry);
 178
 179         if (!git_cache__enabled && cache->used_memory > 0) {
 180                 git_cache_clear(cache);
 181                 return entry;
 182         }
 183
 184         if (!cache_should_store(entry->type, entry->size))
 185                 return entry;
 186
 187         if (git_rwlock_wrlock(&cache->lock) < 0)
 188                 return entry;
 189
 190         /* soften the load on the cache */
 191         if (git_cache__current_storage.val > git_cache__max_storage)
 192                 cache_evict_entries(cache);
 193
 194         pos = git_oidmap_lookup_index(cache->map, &entry->oid);
 195
 196         /* not found */
 197         if (!git_oidmap_valid_index(cache->map, pos)) {
 198                 int rval;
 199
 200                 git_oidmap_insert(cache->map, &entry->oid, entry, &rval);
 201                 if (rval >= 0) {
 202                         git_cached_obj_incref(entry);
 203                         cache->used_memory += entry->size;
 204                         git_atomic_ssize_add(&git_cache__current_storage, (ssize_t)entry->size);
 205                 }
 206         }
 207         /* found */
 208         else {
 209                 git_cached_obj *stored_entry = git_oidmap_value_at(cache->map, pos);
 210
 211                 if (stored_entry->flags == entry->flags) {
 212                         git_cached_obj_decref(entry);
 213                         git_cached_obj_incref(stored_entry);
 214                         entry = stored_entry;
 215                 } else if (stored_entry->flags == GIT_CACHE_STORE_RAW &&
 216                         entry->flags == GIT_CACHE_STORE_PARSED) {
 217                         git_cached_obj_decref(stored_entry);
 218                         git_cached_obj_incref(entry);
 219
 220                         git_oidmap_set_key_at(cache->map, pos, &entry->oid);
 221                         git_oidmap_set_value_at(cache->map, pos, entry);
 222                 } else {
 223                         /* NO OP */
 224                 }
 225         }
 226
 227         git_rwlock_wrunlock(&cache->lock);
 228         return entry;
 229 }
 230
 231 void *git_cache_store_raw(git_cache *cache, git_odb_object *entry)
 232 {
 233         entry->cached.flags = GIT_CACHE_STORE_RAW;
 234         return cache_store(cache, (git_cached_obj *)entry);
 235 }
 236
 237 void *git_cache_store_parsed(git_cache *cache, git_object *entry)
 238 {
 239         entry->cached.flags = GIT_CACHE_STORE_PARSED;
 240         return cache_store(cache, (git_cached_obj *)entry);
 241 }
 242
 243 git_odb_object *git_cache_get_raw(git_cache *cache, const git_oid *oid)
 244 {
 245         return cache_get(cache, oid, GIT_CACHE_STORE_RAW);
 246 }
 247
 248 git_object *git_cache_get_parsed(git_cache *cache, const git_oid *oid)
 249 {
 250         return cache_get(cache, oid, GIT_CACHE_STORE_PARSED);
 251 }
 252
 253 void *git_cache_get_any(git_cache *cache, const git_oid *oid)
 254 {
 255         return cache_get(cache, oid, GIT_CACHE_STORE_ANY);
 256 }
 257
 258 void git_cached_obj_decref(void *_obj)
 259 {
 260         git_cached_obj *obj = _obj;
 261
 262         if (git_atomic_dec(&obj->refcount) == 0) {
 263                 switch (obj->flags) {
 264                 case GIT_CACHE_STORE_RAW:
 265                         git_odb_object__free(_obj);
 266                         break;
 267
 268                 case GIT_CACHE_STORE_PARSED:
 269                         git_object__free(_obj);
 270                         break;
 271
 272                 default:
 273                         git__free(_obj);
 274                         break;
 275                 }
 276         }
 277 }