| From: | "Matthew T(dot) O'Connor" <matthew(at)zeut(dot)net> |
|---|---|
| To: | Mindaugas Riauba <mind(at)bi(dot)lt> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: PostgreSQL strugling during high load |
| Date: | 2005-05-16 02:26:50 |
| Message-ID: | 428804EA.6080609@zeut.net |
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| Lists: | pgsql-performance |
Mindaugas Riauba wrote:
>>The "vacuum cost" parameters can be adjusted to make vacuums fired
>>by pg_autovacuum less of a burden. I haven't got any specific numbers
>>to suggest, but perhaps someone else does.
>>
>>
>
> 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? WAL log
>switch? One WAL file seems to last <1 minute.
>
>
How long are these quite periods? Do the "strom" periods correspond to
pg_autovacuum loops? I have heard from one person who had LOTS of
databases and tables that caused the pg_autovacuum to create a noticable
load just updateing all its stats. The solution in that case was to add
a small delay insidet the inner pg_autovacuum loop.
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