mysql scaling questions

[Gergely CZUCZY]

On Thu, Jan 03, 2008 at 10:52:39PM +0100, Kris Kennaway wrote:
> Gergely CZUCZY wrote:
> 
> >>* Compare to my config file here:
> >>
> >>http://people.freebsd.org/~kris/scaling/my.cnf
> >>
> >>The default mysql config has very poor performance for innodb (you need at least innodb_thread_concurrency = 0 to disable some mysql brain-death).  
> >>Maybe tuning is required for myisam also.
> >>
> >>* Also make sure you are using identical config settings on the two systems.
> >http://phoemix.harmless.hu/mysql/ verify yourself. Only the paths are
> >updated, but the main parameters are just the same.
> 
> You are not in fact using the same config parameters as I am.  When I use your config file I see a large performance loss when I run locally even with 
> innodb.
So, the updated config is here:
http://phoemix.harmless.hu/mysql/my.cnf.kris

I've migrated the values from your config.

And the plot is here:
http://phoemix.harmless.hu/mysql/rw-kris.png

I"ve also plotted a current production system, which crashes around 96 threads in
the test, or so. That's a Linux-2.6.12 and MySQL 5.0.22, so it should be quite unoptimized
compared to any recent version of anything.

As it seems, you were right. These adjustments made a very slight performance boost, around
5%. But it's still lagging behind.

Again, this is MyISAM, not innodb. The "tc4" and "tc16" strings mean the thread_concurrency
is either set to 4 or 16. Your config had 16, but I've googled for it, and some resources
suggested setting that to CPUs*2, and that's 4 in my case.

I've updated the MySQL version on FreeBSD to 5.0.51, and will try to get this version
on linux also, and do a comparision with that one, too.

Sincerely,

Gergely Czuczy
mailto: gergely.czuczy at harmless.hu

-- 
Weenies test. Geniuses solve problems that arise.
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