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Re: High context switches occurring

From: "Anjan Dave" <adave(at)vantage(dot)com>
To: "Scott Marlowe" <smarlowe(at)g2switchworks(dot)com>
Cc: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>,"Vivek Khera" <vivek(at)khera(dot)org>,"Postgresql Performance" <pgsql-performance(at)postgresql(dot)org>
Subject: Re: High context switches occurring
Date: 2005-11-22 23:17:27
Message-ID: 4BAFBB6B9CC46F41B2AD7D9F4BBAF785098E78@vt-pe2550-001.vantage.vantage.com (view raw or flat)
Thread:
Lists: pgsql-performance
Yes, it's turned on, unfortunately it got overlooked during the setup,
and until now...!

It's mostly a 'read' application, I increased the vm.max-readahead to
2048 from the default 256, after which I've not seen the CS storm,
though it could be incidental.

Thanks,
Anjan

-----Original Message-----
From: Scott Marlowe [mailto:smarlowe(at)g2switchworks(dot)com] 
Sent: Tuesday, November 22, 2005 3:38 PM
To: Anjan Dave
Cc: Tom Lane; Vivek Khera; Postgresql Performance
Subject: Re: [PERFORM] High context switches occurring

On Tue, 2005-11-22 at 14:33, Anjan Dave wrote:
> Is there any way to get a temporary relief from this Context Switching
> storm? Does restarting postmaster help?
> 
> It seems that I can recreate the heavy CS with just one SELECT
> statement...and then when multiple such SELECT queries are coming in,
> things just get hosed up until we cancel a bunch of queries...

Is your machine a hyperthreaded one?  Some folks have found that turning
off hyper threading helps.  I knew it made my servers better behaved in
the past.


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