From: | "Gregory S(dot) Williamson" <gsw(at)globexplorer(dot)com> |
---|---|
To: | <creimer(at)brturbo(dot)com(dot)br>, <pgsql-performance(at)postgresql(dot)org> |
Subject: | Re: Context switch storm |
Date: | 2006-11-03 12:50:37 |
Message-ID: | 71E37EF6B7DCC1499CEA0316A256832802B3E801@loki.wc.globexplorer.net |
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Thread: | |
Lists: | pgsql-performance |
Based on what other people have posted, hyperthreading seems not to be beneficial for postgres -- try searching through the archives of this list. (And then turn it off and see if it helps.)
You might also post a few details:
config settings (shared_buffers, work_mem, maintenance_work_mem, wal and checkpoint settings, etc.)
are you using autovacuum ?
all tables are vacuumed and analyzed regularly ? How big are they ? Do they and indexes fit in RAM ?
any particular queries that running and might be related (explain analyze results of them would be useful)
disk configuration
Other processes on this box ?
# of connections to it (I've seen this alone push servers over the edge)
HTH,
Greg Williamson
DBA
GlobeXplorer LLC
-----Original Message-----
From: pgsql-performance-owner(at)postgresql(dot)org on behalf of creimer(at)brturbo(dot)com(dot)br
Sent: Fri 11/3/2006 2:32 AM
To: pgsql-performance(at)postgresql(dot)org
Cc:
Subject: [PERFORM] Context switch storm
Hi,
We've migrated one of our servers from pg 7.4 to 8.1 and from times to times (4 hours) the server start doing a lot of context switching and all transactions become very slow.
The average context switching for this server as vmstat shows is 1 but when the problem occurs it goes to 250000.
CPU and memory usage are ok.
What is producing this context switching storms?
It is a box with 16GB RAM and 4 XEON processors running RedHat Enterprise Linux AS.
Should I disable Hyperthreading?
Thank you in advance!
Reimer
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