What platform is this?
We had similar issue (PG 7.4.7). Raising number of checkpoint segments to 125, seperating the WAL to a different LUN
helped,but it's still not completely gone.
As far as disk I/O is concerned for flushing the buffers out, I am not ruling out the combination of Dell PERC4 RAID
card,and the RH AS 3.0 Update3 being a problem.
Thanks,
Anjan
-----Original Message-----
From: Donald Courtney [mailto:Donald.Courtney@Sun.COM]
Sent: Thu 5/19/2005 12:54 PM
To: Tom Lane
Cc: pgsql-performance@postgresql.org
Subject: Re: [PERFORM] PostgreSQL strugling during high load
Tom
Thanks for the post - I think I am getting this problem for
a synthetic workload at high connection loads. The whole
system seems to stop.
Can you give some examples on what to try out in the .conf file?
I tried
bgwriter_all_percent = 30, 10, and 3
Which I understand to mean 30%, 10% and 3% of the dirty pages should be
written out *between* checkpoints.
I didn't see any change in effect.
/regards
Don C.
Tom Lane wrote:
>"Mindaugas Riauba" <mind@bi.lt> writes:
>
>
>> It looks like that not only vacuum causes our problems. vacuum_cost
>>seems to lower vacuum impact but we are still noticing slow queries "storm".
>>We are logging queries that takes >2000ms to process.
>> And there is quiet periods and then suddenly 30+ slow queries appears in
>>log within the same second. What else could cause such behaviour?
>>
>>
>
>Checkpoints? You should ensure that the checkpoint settings are such
>that checkpoints don't happen too often (certainly not oftener than
>every five minutes or so), and make sure the bgwriter is configured
>to dribble out dirty pages at a reasonable rate, so that the next
>checkpoint doesn't have a whole load of stuff to write.
>
> regards, tom lane
>
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