From: Balkrishna Sharma <b_ki@hotmail.com>
To: kevin.grittner@wicourts.gov
To: pgsql-admin@postgresql.org
Subject: Re: How to find if a SELECT is reading from buffer or disk ?
Date: Tue, 25 May 2010 14:01:22 -0400
Message-ID: <BAY149-w3701A07CB4C59BEAB6CF88F0E80@phx.gbl> (raw)
In-Reply-To: <4BFBC9A40200002500031A64@gw.wicourts.gov>
References: <BAY149-w19CB46743B9D1EC9D68760F0E80@phx.gbl>
<4BFBC9A40200002500031A64@gw.wicourts.gov>
I am on Fedora 12 (x86_64). Will eventually be on RHE.
> Date: Tue, 25 May 2010 12:59:16 -0500
> From: Kevin.Grittner@wicourts.gov
> To: b_ki@hotmail.com; pgsql-admin@postgresql.org
> Subject: Re: [ADMIN] How to find if a SELECT is reading from buffer or disk ?
>
> Balkrishna Sharma <b_ki@hotmail.com> wrote:
>
> > I am increasing the shared_buffer size in postgresql.conf and want
> > to measure its effect on READ. In essence I want to know if the
> > SELECT queries I am firing repeatedly is reading from the buffer
> > or going directly to the disk.
>
> There's a third option -- PostgreSQL reads and writes will normally
> go through the OS cache.
>
> > Right now I am just looking at execution time of the SELECTs and
> > trying to conclude. But there should be a direct way to see where
> > the SELECT reads from.
> > How can I accomplish this ?
>
> You didn't mention your OS. There's usually a way to monitor disk
> I/O built in to the OS. I usually start with:
>
> vmstat 1
>
> -Kevin
>
> --
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To: pgsql-admin@postgresql.org
Cc: b_ki@hotmail.com, kevin.grittner@wicourts.gov
Subject: Re: How to find if a SELECT is reading from buffer or disk ?
In-Reply-To: <BAY149-w3701A07CB4C59BEAB6CF88F0E80@phx.gbl>
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