MySQL Performance
Troy Settle
troy at psknet.com
Tue Aug 2 16:43:43 GMT 2005
Thanks to all for the feedback. Looking at the status, there were 7
slow queries. I've enabled logging and re-started the server. Now I
wait a few weeks to see what, if anything, happens. Of course, by that
time, I hope to have a dedicated MySQL server up and running, though I'm
not sure I'll want to run my mail server off a remote database.
Thanks again,
--
Troy Settle
Pulaski Networks
http://www.psknet.com
866.477.5638
James Ryan wrote:
> Try enabling slow query logging, as well as maybe try to isolate if the
> load is coming from any particular query...
>
> If you are performing joins on the 1k+ rows table, maybe MySQL has ran
> out of memory and is copying the query results to a tmp table on the
> disk. Sometimes this can cause a jump in CPU usage... You can
> determine if this is the case by mysqladmin processlist; it will say
> something like "Copying to tmp table".
>
> Check for slow queries though...
>
> Cheers,
> James
>
> Troy Settle wrote:
>
>>
>> I've a 4-STABLE box on a Dual Xeon w/4GB and U320 RAID:
>>
>> 4.11-STABLE FreeBSD 4.11-STABLE #7: Fri Mar 11 20:24:25 EST 2005
>> 10:05AM up 55 days, 14:38, 3 users, load averages: 1.07, 1.10, 1.13
>>
>> Running on this box, is MySQL 4.0.23a (a little outdated, I know).
>> This MySQL server seems to run fine as long as I watch it, but as soon
>> as I turn my head for a moment, it jumps up to ~97% CPU usage:
>>
>> 508 mysql 63 0 99M 51660K CPU0 0 306.9H 97.46% 97.46% mysqld
>>
>> It doesn't appear to be an IO issue, 300 samples from iostat show a
>> max of 0.31 MB/s.
>>
>> It also doesn't appear to be a memory issue:
>>
>> 867M Active, 2354M Inact, 320M Wired, 192M Cache, 199M Buf, 40M Free
>> Swap: 4096M Total, 16K Used, 4096M Free
>>
>> Through a number of samples from sockstat(1), I see ~20 connections to
>> mysql at any given time. 5 for Courier's authdaemon, 3 for Exim, and
>> ~12 for Apache/PHP. There are intermitant connections from Windows
>> clients using MyODBC, but none are persistant. Restarting any/all of
>> these processes does not cause mysql to ease up on the CPU. Only
>> restarting MySQL will buy releif, but after a few weeks, it's right
>> back to 97% CPU usage.
>>
>> The machine itself is completely responsive, mysql is completely
>> responsive. The tables in question are flat, with only a few thousand
>> entries in the largest. Queries range from simple to semi-complex.
>>
>> I can't identify the source of the load. Can anyone help? What
>> should I be looking at?
>>
>> Thanks,
>>
>> --
>> Troy Settle
>> Pulaski Networks
>> http://www.psknet.com
>> 866.477.5638
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