mysql scaling questions

[Kris Kennaway]

Gergely CZUCZY wrote:

>> I appreciate that you might be constrained by local requirements, but it's really not meaningful to compare different mysql versions if 
>> your goal is to study OS performance.
> It'd be a PITA to install the both versions. Maybe now, that the ports freeze is over, i can
> do something. But honestly, every mysql version was faster on linux, than eny on FreeBSD,
> even the .22 one was faster. We start work on Jan02, I will see what can I do.

Regardless, we need a stable baseline to compare to.

>> * What database engine are you using?  I have only tested with innodb but maybe you are using myisam?  Please provide your exact 
>> sysbench command lines.
> MyISAM, of course. InnoDB is not any good with replication, and we need backup.

OK.  I tested briefly and InnoDB is almost 20 times faster on my tests 
with default myisam settings.  myisam runs into the usual serious mysql 
scaling problems at concurrency > 8 threads (contention within the mysql 
application, not a FreeBSD issue).

Still waiting for your sysbench command lines :)

>> * 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.

OK, I will take your word for it.

>> * With the above, please compare read-only mode also (I think Jeff already asked you about this but I didnt see a reply).  That will 
>> allow us to calibrate what is going on.
> http://phoemix.harmless.hu/mysql/ro-all.png
> The graph is mistitled as Read-write, but it's a readonly test.

OK.

Kris