When grilled further on (Wed, 19 May 2004 21:20:20 -0400 (EDT)),
Bruce Momjian <pgman@candle.pha.pa.us> confessed:
>
> Did we ever come to a conclusion about excessive SMP context switching
> under load?
>
I just figured out what was causing the problem on my system Monday. I'm using
the pg_autovacuum daemon, and it was not vacuuming my db. I've no idea why and
didn't get a chance to investigate.
This lack of vacuuming was causing a huge number of context switches and query
delays. the queries that normally take .1 seconds were taking 11 seconds, and
the context switches were averaging 160k/s, peaking at 190k/s
Unfortunately, I was under pressure to fix the db at the time so I didn't get a
chance to play with the patch.
I restarted the vacuum daemon, and will keep an eye on it to see if it behaves.
If the problem re-occurs, is it worth while to attempt the different patch
delay settings?
Cheers,
Rob
--
19:45:40 up 21 days, 2:30, 4 users, load average: 2.03, 2.09, 2.06
Linux 2.6.5-01 #7 SMP Fri Apr 16 22:45:31 MDT 2004
