Re: Context switch storm - Mailing list pgsql-performance

From Gregory S. Williamson
Subject Re: Context switch storm
Date
Msg-id 71E37EF6B7DCC1499CEA0316A256832802B3E801@loki.wc.globexplorer.net
Whole thread Raw
In response to Context switch storm  (creimer@brturbo.com.br)
List pgsql-performance
Based on what other people have posted, hyperthreading seems not to be beneficial for postgres -- try searching through
thearchives 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@postgresql.org on behalf of creimer@brturbo.com.br
Sent:    Fri 11/3/2006 2:32 AM
To:    pgsql-performance@postgresql.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
contextswitching 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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