From d460f1689da6081ea06ee25e0c7553c74dd50c30 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.h | 1 + 1 file changed, 1 insertion(+) (limited to 'sql/mysqld.h') diff --git a/sql/mysqld.h b/sql/mysqld.h index eb885417da3..67e39b6a46b 100644 --- a/sql/mysqld.h +++ b/sql/mysqld.h @@ -181,6 +181,7 @@ extern ulonglong max_binlog_cache_size, max_binlog_stmt_cache_size; extern ulong max_binlog_size, max_relay_log_size; extern ulong opt_binlog_rows_event_max_size; extern ulong rpl_recovery_rank, thread_cache_size; +extern ulong stored_program_cache_size; extern ulong back_log; extern char language[FN_REFLEN]; extern "C" MYSQL_PLUGIN_IMPORT ulong server_id; -- cgit v1.2.1