Please add this patch (http://mysql.bkbits.net:8080/mysql-5.0/gnupatch@4552a85ddHCqJ_0Ar7GHnQkDE54iAg) to fix this bug (http://bugs.mysql.com/bug.php?id=15815).
Eh, the upstream bug is so messy that I'd rather not apply such patches blindly until upstream includes them.
Patch already in mysql 5.0.30. http://dev.mysql.com/doc/refman/5.0/en/releasenotes-es-5-0-30.html InnoDB showed substandard performance with multiple queries running concurrently. (Bug#15815) So please add patch to ebuild.
Any news?
sorry for the late answer, dev-db/mysql-5.0.30 is in the tree, sources are on our mirrors too, this should fix the issue, please reopen if I missed something.