Description of problem: The Customer is experiencing problems with MySQL and can relate to the MySql bug below: Bug #15815 Very poor performance with multiple queries running concurrently -> http://bugs.mysql.com/bug.php ?id=15815 The problem is: Query starts to take significantly longer if multiple queries are executed at once. Version-Release number of selected component (if applicable): 5.0.45 How reproducible: 100% Steps to Reproduce: CREATE TABLE `b` ( `child_id` int(10) unsigned NOT NULL default '0', `b` char(20) default NULL, KEY `child_id` (`child_id`) ) ENGINE=InnoDB Populate table with 100.000+ of rows, but make sure it still fits in buffer pool. insert into b (child_id) values (0); insert into b (child_id) values (0); insert into b (child_id) values (0); insert into b (child_id) values (0); insert into b (child_id) values (0); insert into b select * from b; .... insert into b select * from b; (repeat while you get enough rows) Create 1.sql file: use test; select sql_calc_found_rows * from b limit 5; select sql_calc_found_rows * from b limit 5; select sql_calc_found_rows * from b limit 5; select sql_calc_found_rows * from b limit 5; select sql_calc_found_rows * from b limit 5; Run 1 copy: create 1.sh: cat 1.sql | time mysql > /dev/null Run 4 copies: create 4.sh: ./1.sh & ./1.sh & ./1.sh & ./1.sh & Run 1.sh and 4.sh to see what happens for 1 and 4 connections. Actual results: performance drops, cpu usage increases on 1 cpu. Expected results: increased performance and utilize all cpus Additional info: http://bugs.mysql.com/bug.php?id=15815 This changeset contains necessary patches to fix innodb scaling http://mysql.bkbits.net:8080/mysql-5.0/?PAGE=patch&REV=4552a85ddHCqJ_0Ar7GHnQkDE54iAg Thanks
This also applies to RHEL5.1 (stable) with all updates. Why is this bug given a "low" severity? It currently makes any Red Hat shipped version of MySQL practically unusable for any scenario where InnoDB is used. This bug forces us to use mysql.com provided community-releases as it is. I was hoping it would be resolved in RHEL5.2, but if this still applies to the package currently included in 5.3 my hopes are not up. Some priority would be welcome. Regards Denis
Denis, Thanks for the update -- Ive raised the severity/priority flags. May I also suggest that if you have a support contract with Red Hat that you file a support request referencing this BZ as well? Thank you, Adam
Adam, I have already done this, is it enough to include a link to this BZ bugid in the description? Regards Denis
Hi Denis, That should be enough -- our engineers will triage that support request up to the appropriate backline engineers to be handled. Thank you for your support. Adam
If you're seeing this in 5.0.45 then that upstream fix was already applied, and you're going to need to talk to MySQL AB about the problem --- fixing such things is far beyond my knowledge of that code.
I am sorry about the misunderstanding here. I do not see this behaviour with 5.0.45, but with 5.0.22 which is what RHEL5.1 ships. If this means I should create a separate bug instead, then I will proceed to do so. Again sorry. Denis
5.0.45 is scheduled to go out in RHEL 5.2, so you just need to wait a bit ...
Can someone with the necessary permissions please change the Version field from 5.3 to 5.1. That way it will not mislead any more people (like what happened in Comment #1).
Fixed in RHEL 5.2 update.