1 /* svn_cache_config.c : configuration of internal caches
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9 * "License"); you may not use this file except in compliance
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12 * http://www.apache.org/licenses/LICENSE-2.0
14 * Unless required by applicable law or agreed to in writing,
15 * software distributed under the License is distributed on an
16 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
17 * KIND, either express or implied. See the License for the
18 * specific language governing permissions and limitations
20 * ====================================================================
23 #include <apr_atomic.h>
25 #include "svn_cache_config.h"
26 #include "private/svn_atomic.h"
27 #include "private/svn_cache.h"
29 #include "svn_pools.h"
31 /* The cache settings as a process-wide singleton.
33 static svn_cache_config_t cache_settings =
35 /* default configuration:
37 * Please note that the resources listed below will be allocated
38 * PER PROCESS. Thus, the defaults chosen here are kept deliberately
39 * low to still make a difference yet to ensure that pre-fork servers
40 * on machines with small amounts of RAM aren't severely impacted.
42 0x1000000, /* 16 MB for caches.
43 * If you are running a single server process,
44 * you may easily increase that to 50+% of your RAM
45 * using svn_fs_set_cache_config().
47 16, /* up to 16 files kept open.
48 * Most OS restrict the number of open file handles to
49 * about 1000. To minimize I/O and OS overhead, values
50 * of 500+ can be beneficial (use svn_fs_set_cache_config()
51 * to change the configuration).
52 * When running with a huge in-process cache, this number
53 * has little impact on performance and a more modest
54 * value (< 100) may be more suitable.
57 FALSE /* assume multi-threaded operation.
58 * Because this simply activates proper synchronization
59 * between threads, it is a safe default.
62 TRUE /* single-threaded is the only supported mode of operation */
66 /* Get the current FSFS cache configuration. */
67 const svn_cache_config_t *
68 svn_cache_config_get(void)
70 return &cache_settings;
73 /* Initializer function as required by svn_atomic__init_once. Allocate
74 * the process-global (singleton) membuffer cache and return it in the
75 * svn_membuffer_t * in *BATON. UNUSED_POOL is unused and should be NULL.
78 initialize_cache(void *baton, apr_pool_t *unused_pool)
80 svn_membuffer_t **cache_p = baton;
81 svn_membuffer_t *cache = NULL;
83 apr_uint64_t cache_size = cache_settings.cache_size;
88 /* auto-allocate cache */
89 apr_allocator_t *allocator = NULL;
90 apr_pool_t *pool = NULL;
92 if (apr_allocator_create(&allocator))
95 /* Ensure that we free partially allocated data if we run OOM
96 * before the cache is complete: If the cache cannot be allocated
97 * in its full size, the create() function will clear the pool
98 * explicitly. The allocator will make sure that any memory no
99 * longer used by the pool will actually be returned to the OS.
101 * Please note that this pool and allocator is used *only* to
102 * allocate the large membuffer. All later dynamic allocations
103 * come from other, temporary pools and allocators.
105 apr_allocator_max_free_set(allocator, 1);
107 /* don't terminate upon OOM but make pool return a NULL pointer
108 * instead so we can disable caching gracefully and continue
109 * operation without membuffer caches.
111 apr_pool_create_ex(&pool, NULL, NULL, allocator);
114 apr_allocator_owner_set(allocator, pool);
116 err = svn_cache__membuffer_cache_create(
118 (apr_size_t)cache_size,
119 (apr_size_t)(cache_size / 10),
121 ! svn_cache_config_get()->single_threaded,
125 /* Some error occurred. Most likely it's an OOM error but we don't
126 * really care. Simply release all cache memory and disable caching
131 svn_pool_destroy(pool);
133 /* Document that we actually don't have a cache. */
134 cache_settings.cache_size = 0;
136 return svn_error_trace(err);
146 /* Access the process-global (singleton) membuffer cache. The first call
147 * will automatically allocate the cache using the current cache config.
148 * NULL will be returned if the desired cache size is 0 or if the cache
149 * could not be created for some reason.
152 svn_cache__get_global_membuffer_cache(void)
154 static svn_membuffer_t *cache = NULL;
155 static svn_atomic_t initialized = 0;
158 = svn_atomic__init_once(&initialized, initialize_cache, &cache, NULL);
161 /* no caches today ... */
162 svn_error_clear(err);
170 svn_cache_config_set(const svn_cache_config_t *settings)
172 cache_settings = *settings;