From: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
---|---|
To: | Wei Weng <wweng(at)kencast(dot)com> |
Cc: | pgsql-performance(at)postgresql(dot)org |
Subject: | Re: swapping? |
Date: | 2002-11-14 14:56:22 |
Message-ID: | 200211141456.gAEEuNL27864@candle.pha.pa.us |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-performance |
Usually vmstat shows page ins. I also write a paper on this:
The techdocs site has other stuff, see "Optimzation" section:
http://techdocs.postgresql.org/
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Wei Weng wrote:
> How do you notice that if a system started swapping or not?
>
> Thanks
>
> On Thu, 2002-11-14 at 09:37, Shridhar Daithankar wrote:
> > On 14 Nov 2002 at 10:30, Wei Weng wrote:
> >
> > > The term had been mentioned often enough on this mailing list. Can
> > > someone enlighten me with some description or a URL where I can read on?
> > > And why is it important to postgresql database performace?
> >
> > When programs request more memory than available, OS 'swaps' some memory to
> > special area on disk and make the memory available. To programs, it gives
> > appearance that nearly infinite memory is available.
> >
> > Unfortunately disk are hell slower than RAM and hence swapping slows things
> > down as it takes much to swap in to disk and swap out of disk. Since OS does
> > not care which programs get swapped, it is possible that postgresql instance
> > can get swapped. That slows down effective memory access to knees..
> >
> > That's why for good performance, a serve should never swap..
> >
> > Bye
> > Shridhar
> >
> > --
> > Peterson's Admonition: When you think you're going down for the third time --
> > just remember that you may have counted wrong.
> >
> >
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> --
> Wei Weng
> Network Software Engineer
> KenCast Inc.
>
>
>
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>
--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 359-1001
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