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/sql_prepare.cc | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'sql/sql_prepare.cc') diff --git a/sql/sql_prepare.cc b/sql/sql_prepare.cc index 48b6886f6f2..cfdf7d27e58 100644 --- a/sql/sql_prepare.cc +++ b/sql/sql_prepare.cc @@ -2195,6 +2195,9 @@ void mysqld_stmt_prepare(THD *thd, const char *packet, uint packet_length) thd->protocol= save_protocol; + sp_cache_enforce_limit(thd->sp_proc_cache, stored_program_cache_size); + sp_cache_enforce_limit(thd->sp_func_cache, stored_program_cache_size); + /* check_prepared_statemnt sends the metadata packet in case of success */ DBUG_VOID_RETURN; } @@ -2560,6 +2563,9 @@ void mysqld_stmt_execute(THD *thd, char *packet_arg, uint packet_length) stmt->execute_loop(&expanded_query, open_cursor, packet, packet_end); thd->protocol= save_protocol; + sp_cache_enforce_limit(thd->sp_proc_cache, stored_program_cache_size); + sp_cache_enforce_limit(thd->sp_func_cache, stored_program_cache_size); + /* Close connection socket; for use with client testing (Bug#43560). */ DBUG_EXECUTE_IF("close_conn_after_stmt_execute", vio_close(thd->net.vio);); -- cgit v1.2.1