From 97883d3c0498dfaa17f6f7cbefa373b7cd2c72a3 Mon Sep 17 00:00:00 2001 From: Dmitry Shulga Date: Wed, 25 Jan 2012 15:59:30 +0600 Subject: Fixed bug#11753187 (formerly known as bug 44585): SP_CACHE BEHAVES AS MEMORY LEAK. Background: - There are caches for stored functions and stored procedures (SP-cache); - There is no similar cache for events; - Triggers are cached together with TABLE objects; - Those SP-caches are per-session (i.e. specific to each session); - A stored routine is represented by a sp_head-instance internally; - SP-cache basically contains sp_head-objects of stored routines, which have been executed in a session; - sp_head-object is added into the SP-cache before the corresponding stored routine is executed; - SP-cache is flushed in the end of the session. The problem was that SP-cache might grow without any limit. Although this was not a pure memory leak (the SP-cache is flushed when session is closed), this is still a problem, because the user might take much memory by executing many stored routines. The patch fixes this problem in the least-intrusive way. A soft limit (similar to the size of table definition cache) is introduced. To represent such limit the new runtime configuration parameter 'stored_program_cache' is introduced. The value of this parameter is stored in the new global variable stored_program_cache_size that used to control the size of SP-cache to overflow. The parameter 'stored_program_cache' limits number of cached routines for each thread. It has the following min/default/max values given from support: min = 256, default = 256, max = 512 * 1024. Also it should be noted that this parameter limits the size of each cache (for stored procedures and for stored functions) separately. The SP-cache size is checked after top-level statement is parsed. If SP-cache size exceeds the limit specified by parameter 'stored_program_cache' then SP-cache is flushed and memory allocated for cache objects is freed. Such approach allows to flush cache safely when there are dependencies among stored routines. sql/mysqld.cc: Added global variable stored_program_cache_size to store value of configuration parameter 'stored-program-cache'. sql/mysqld.h: Added declaration of global variable stored_program_cache_size. sql/sp_cache.cc: Extended interface for sp_cache by adding helper routine sp_cache_enforce_limit to control size of stored routines cache for overflow. Also added method enforce_limit into class sp_cache that implements control of cache size for overflow. sql/sp_cache.h: Extended interface for sp_cache by adding standalone routine sp_cache_enforce_limit to control size of stored routines cache for overflow. sql/sql_parse.cc: Added flush of sp_cache after processing of next sql-statement received from a client. sql/sql_prepare.cc: Added flush of sp_cache after preparation/execution of next prepared sql-statement received from a client. sql/sys_vars.cc: Added support for configuration parameter stored-program-cache. --- sql/sp_cache.h | 1 + 1 file changed, 1 insertion(+) (limited to 'sql/sp_cache.h') diff --git a/sql/sp_cache.h b/sql/sp_cache.h index 39448568a76..db70066587a 100644 --- a/sql/sp_cache.h +++ b/sql/sp_cache.h @@ -62,5 +62,6 @@ sp_head *sp_cache_lookup(sp_cache **cp, sp_name *name); void sp_cache_invalidate(); void sp_cache_flush_obsolete(sp_cache **cp, sp_head **sp); ulong sp_cache_version(); +void sp_cache_enforce_limit(sp_cache *cp, ulong upper_limit_for_elements); #endif /* _SP_CACHE_H_ */ -- cgit v1.2.1