mysql scaling questions

[Kris Kennaway]

Gergely CZUCZY wrote:
> 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
> 

OK.  The caching problem with myisam is unrelated to the other config 
changes then.

Kris