Bug #20113 Performance degredation on 8 way system ( 4x Opteron 875's )
Submitted: 28 May 2006 15:51 Modified: 31 May 2006 5:48
Reporter: Matt Heler Email Updates:
Status: Duplicate Impact on me:
None 
Category:MySQL Server: InnoDB storage engine Severity:S5 (Performance)
Version:5.0.21 OS:Linux (Fedora Core5)
Assigned to: Assigned Account CPU Architecture:Any

[28 May 2006 15:51] Matt Heler 
Description:
An upgrade was performed last night that increased the cpu's from 2 Opteron 875's ( dual core ) to 4 . After the upgrade performance on MySQL degraded immensily. 

We are using Innodb tables, and the latest MySQL 5.0 release.

How to repeat:
Install a 4 way Opteron 875 system ?
[30 May 2006 15:36] Heikki Tuuri 
Matt,

this is probably a duplicate of http://bugs.mysql.com/bug.php?id=15815

Try setting innodb_thread_concurrency to 4 or even lower.

Regards,

Heikki
[30 May 2006 15:54] Matt Heler 
Theese are dual cores, so would I use 4 or 8 ? 

Thanks,
[30 May 2006 15:57] Heikki Tuuri 
Matt,

you need to test. You may need to use even value 1 if there is serious thread thrashing.

Regards,

Heikki
[31 May 2006 5:48] Matt Heler 
I can confirm that lowering thread concurrency 4 seems to alleviate many of the problems we were seeing. Thanks