From 139c8ed5915385a914fce8d87764a3cf3d334e7e Mon Sep 17 00:00:00 2001 From: Jon Olav Hauglid Date: Tue, 25 Sep 2012 13:09:53 +0200 Subject: [PATCH] Bug#14621627 THREAD CACHE IS UNFAIR When a client connects to a MySQL server, first a THD object is created. If there are any idle server threads waiting, the THD object is then added to a list and a server thread is woken up. This thread then retrieves the THD object from the list and starts executing. The problem was that this list of THD objects waiting for a server thread, was not working in a FIFO fashion, but rather LIFO. This is unfair, as it means that the last THD added (=last client connected) will be assigned a server thread first. Note however that for this to be a problem, several clients must be able to connect and have THD objects constructed before any server threads manages to be woken up. This is not a very likely scenario. This patch fixes the problem by changing the THD list to work FIFO rather than LIFO. This is the 5.1/5.5 version of the patch. --- sql/mysqld.cc | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/sql/mysqld.cc b/sql/mysqld.cc index bc8d4162272..11e756381ab 100644 --- a/sql/mysqld.cc +++ b/sql/mysqld.cc @@ -4808,7 +4808,7 @@ void create_thread_to_handle_connection(THD *thd) if (cached_thread_count > wake_thread) { /* Get thread from cache */ - thread_cache.append(thd); + thread_cache.push_back(thd); wake_thread++; pthread_cond_signal(&COND_thread_cache); }