Re: Performance Tuning and Disk Cache - Mailing list pgsql-performance

From David Boreham
Subject Re: Performance Tuning and Disk Cache
Date
Msg-id 45FD5A2D.2090307@boreham.org
Whole thread Raw
In response to Performance Tuning and Disk Cache  (Barry Moore <barry.moore@genetics.utah.edu>)
Responses Re: Performance Tuning and Disk Cache  ("Rangarajan Vasudevan" <ranga@asterdata.com>)
List pgsql-performance
Barry Moore wrote:

> I have a very slow query that I'm trying to tune.  I think my
> performance tuning is being complicated by the system's page cache.
>
> If a run the query after the system has been busy with other tasks
> for quite a long time then the query can take up to 8-10 minutes to
> complete.  If I then rerun the same query it will complete in a
> couple of seconds.
>
> Does anyone know how I can repeatedly run the same query in the
> "worst case scenario" of no postgres data in the disk cache (e.g.,
> clear the page cache or force it to be ignored)?

In my experience the only 100% reliable way to do this is to reboot the
machine.



pgsql-performance by date:

Previous
From: "hubert depesz lubaczewski"
Date:
Subject: Re: Performance Tuning and Disk Cache
Next
From: "Rangarajan Vasudevan"
Date:
Subject: Re: Performance Tuning and Disk Cache