1/* svn_cache_config.c : configuration of internal caches
2 *
3 * ====================================================================
4 *    Licensed to the Apache Software Foundation (ASF) under one
5 *    or more contributor license agreements.  See the NOTICE file
6 *    distributed with this work for additional information
7 *    regarding copyright ownership.  The ASF licenses this file
8 *    to you under the Apache License, Version 2.0 (the
9 *    "License"); you may not use this file except in compliance
10 *    with the License.  You may obtain a copy of the License at
11 *
12 *      http://www.apache.org/licenses/LICENSE-2.0
13 *
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
19 *    under the License.
20 * ====================================================================
21 */
22
23#include <apr_atomic.h>
24
25#include "svn_cache_config.h"
26#include "private/svn_atomic.h"
27#include "private/svn_cache.h"
28
29#include "svn_pools.h"
30
31/* The cache settings as a process-wide singleton.
32 */
33static svn_cache_config_t cache_settings =
34  {
35    /* default configuration:
36     *
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.
41     */
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().
46                  */
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.
55                  */
56#if APR_HAS_THREADS
57    FALSE        /* assume multi-threaded operation.
58                  * Because this simply activates proper synchronization
59                  * between threads, it is a safe default.
60                  */
61#else
62    TRUE         /* single-threaded is the only supported mode of operation */
63#endif
64};
65
66/* Get the current FSFS cache configuration. */
67const svn_cache_config_t *
68svn_cache_config_get(void)
69{
70  return &cache_settings;
71}
72
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.
76 */
77static svn_error_t *
78initialize_cache(void *baton, apr_pool_t *unused_pool)
79{
80  svn_membuffer_t **cache_p = baton;
81  svn_membuffer_t *cache = NULL;
82
83  apr_uint64_t cache_size = cache_settings.cache_size;
84  if (cache_size)
85    {
86      svn_error_t *err;
87
88      /* auto-allocate cache */
89      apr_allocator_t *allocator = NULL;
90      apr_pool_t *pool = NULL;
91
92      if (apr_allocator_create(&allocator))
93        return SVN_NO_ERROR;
94
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.
100       *
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.
104       */
105      apr_allocator_max_free_set(allocator, 1);
106
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.
110       */
111      apr_pool_create_ex(&pool, NULL, NULL, allocator);
112      if (pool == NULL)
113        return SVN_NO_ERROR;
114      apr_allocator_owner_set(allocator, pool);
115
116      err = svn_cache__membuffer_cache_create(
117          &cache,
118          (apr_size_t)cache_size,
119          (apr_size_t)(cache_size / 10),
120          0,
121          ! svn_cache_config_get()->single_threaded,
122          FALSE,
123          pool);
124
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
127       */
128      if (err)
129        {
130          /* Memory cleanup */
131          svn_pool_destroy(pool);
132
133          /* Document that we actually don't have a cache. */
134          cache_settings.cache_size = 0;
135
136          return svn_error_trace(err);
137        }
138
139      /* done */
140      *cache_p = cache;
141    }
142
143  return SVN_NO_ERROR;
144}
145
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.
150 */
151svn_membuffer_t *
152svn_cache__get_global_membuffer_cache(void)
153{
154  static svn_membuffer_t *cache = NULL;
155  static svn_atomic_t initialized = 0;
156
157  svn_error_t *err
158    = svn_atomic__init_once(&initialized, initialize_cache, &cache, NULL);
159  if (err)
160    {
161      /* no caches today ... */
162      svn_error_clear(err);
163      return NULL;
164    }
165
166  return cache;
167}
168
169void
170svn_cache_config_set(const svn_cache_config_t *settings)
171{
172  cache_settings = *settings;
173}
174
175