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Re: High context switches occurring

From: "Anjan Dave" <adave(at)vantage(dot)com>
To: "Simon Riggs" <simon(at)2ndquadrant(dot)com>
Cc: "Scott Marlowe" <smarlowe(at)g2switchworks(dot)com>,"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: 2005-11-23 18:33:09
Message-ID: 4BAFBB6B9CC46F41B2AD7D9F4BBAF785098E7B@vt-pe2550-001.vantage.vantage.com (view raw or flat)
Thread:
Lists: pgsql-performance
The offending SELECT query that invoked the CS storm was optimized by
folks here last night, so it's hard to say if the VM setting made a
difference. I'll give it a try anyway.

Thanks,
Anjan

-----Original Message-----
From: Simon Riggs [mailto:simon(at)2ndquadrant(dot)com] 
Sent: Wednesday, November 23, 2005 1:14 PM
To: Anjan Dave
Cc: Scott Marlowe; Tom Lane; Vivek Khera; Postgresql Performance
Subject: Re: [PERFORM] High context switches occurring

On Tue, 2005-11-22 at 18:17 -0500, Anjan Dave wrote:

> 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.

Can you verify this, please?

Turn it back down again, try the test, then reset and try the test.

If that is a repeatable way of recreating one manifestation of the
problem then we will be further ahead than we are now.

Thanks,

Best Regards, Simon Riggs



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