Re: PostgreSQL strugling during high load - Mailing list pgsql-performance
From | Donald Courtney |
---|---|
Subject | Re: PostgreSQL strugling during high load |
Date | |
Msg-id | 428CDB07.2030503@sun.com Whole thread Raw |
In response to | Re: PostgreSQL strugling during high load ("Anjan Dave" <adave@vantage.com>) |
List | pgsql-performance |
Anjan Dave wrote: >What platform is this? > > > Its a DELL RH 4 with the xlog on a seperate external mounted file system. The data directory is on a external mounted file system as well. >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. > > > I'll try raising the number. I guess the bg* config variables don't do much? thanks >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 > > > >---------------------------(end of broadcast)--------------------------- > >TIP 1: subscribe and unsubscribe commands go to majordomo@postgresql.org > > > > > > > ---------------------------(end of broadcast)--------------------------- > TIP 7: don't forget to increase your free space map settings > > >---------------------------(end of broadcast)--------------------------- >TIP 3: if posting/reading through Usenet, please send an appropriate > subscribe-nomail command to majordomo@postgresql.org so that your > message can get through to the mailing list cleanly > >
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