On file_handle_cache branch:
Limit the number of open file handles on a per-process basis instead of
per-cache.
* subversion/libsvn_subr/svn_file_handle_cache.c
clarify global commentary
(global_handle_count): new global, shared variable
(internal_file_open, internal_close_file): update the global counter as well
(auto_close_oldest): limit handle count against the _global_ counter
(close_all_handles): new "destructor" to unsure update of the global counter
(svn_file_handle_cache__create_cache): register destructor
git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/file-handle-cache@1220463 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/subversion/libsvn_subr/svn_file_handle_cache.c b/subversion/libsvn_subr/svn_file_handle_cache.c
index 88d9cb9..c7fc7aa 100644
--- a/subversion/libsvn_subr/svn_file_handle_cache.c
+++ b/subversion/libsvn_subr/svn_file_handle_cache.c
@@ -25,6 +25,7 @@
#include "private/svn_file_handle_cache.h"
#include "private/svn_mutex.h"
+#include "private/svn_atomic.h"
#include "svn_private_config.h"
#include "svn_pools.h"
#include "svn_io.h"
@@ -64,9 +65,9 @@
* without the application being aware of it, no distinction is being made
* between read-after-write, write-after-read or others.
*
- * For similar reasons, an application may want to close all idle handles
- * explicitly, i.e. without opening new ones. svn_file_handle_cache__flush
- * is the function to call in that case.
+ * It is the application's task to inform the cache that some write has
+ * occured and the respective file handles shall be removed from the cache.
+ * svn_file_handle_cache__flush is the function to call in that case.
*/
/* Size of the APR per-file data buffer. We don't rely on this value to
@@ -76,6 +77,9 @@
*/
#define FILE_BUFFER_SIZE 0x1000
+/* Aggregated open file handle count over all cache instances. */
+static volatile svn_atomic_t global_handle_count = 0;
+
/* forward-declarations */
typedef struct cache_entry_t cache_entry_t;
typedef struct entry_link_t entry_link_t;
@@ -402,6 +406,7 @@
*/
append_to_list(&cache->used_entries, &entry->global_link);
append_to_list(&cache->idle_entries, &entry->idle_link);
+ svn_atomic_inc(&global_handle_count);
/* link with other entries for the same file in the index, or add it
* to the index if no entry for this file name exists so far */
@@ -464,6 +469,7 @@
/* remove entry from the idle and global list */
remove_from_list(&cache->idle_entries, &entry->idle_link);
remove_from_list(&cache->used_entries, &entry->global_link);
+ svn_atomic_dec(&global_handle_count);
/* actually close the file handle. */
if (entry->file)
@@ -559,7 +565,7 @@
static svn_error_t *
auto_close_oldest(svn_file_handle_cache_t *cache)
{
- return cache->used_entries.count > cache->max_used_count
+ return svn_atomic_read(&global_handle_count) > cache->max_used_count
? close_oldest_idle(cache)
: SVN_NO_ERROR;
}
@@ -887,6 +893,23 @@
return SVN_NO_ERROR;
}
+/* Close all remaining cached file handles.
+ */
+static apr_status_t
+close_all_handles(void *cache_void)
+{
+ svn_file_handle_cache_t *cache = cache_void;
+
+ /* There is no apr_atomic_sub and *_add requires an unsigned value.
+ * Thus, we can't use apr_atomic_add portably to mimic *_sub.
+ */
+ size_t i;
+ for (i = cache->used_entries.count; i > 0; --i)
+ svn_atomic_dec(&global_handle_count);
+
+ return APR_SUCCESS;
+}
+
/* Creates a new file handle cache in CACHE. Up to MAX_HANDLES file handles
* will be kept open. All cache-internal memory allocations during the caches'
* lifetime will be done from POOL.
@@ -918,6 +941,12 @@
svn_mutex__init(&new_cache->mutex, thread_safe, pool);
+ /* ensure we update global_handle_count correctly. */
+ apr_pool_cleanup_register(pool,
+ new_cache,
+ close_all_handles,
+ apr_pool_cleanup_null);
+
/* done */
*cache = new_cache;
return SVN_NO_ERROR;
