Re: swapping? - Mailing list pgsql-performance

I hope this doesn't sound too stupid. :)

1: I see sort_mem setting in my postgresql.conf, what is the "buffer
size" people often talk about?

2: What is the unit of sort_mem in postgresql.conf? In my basic(default)
installation, I have sort_mem=512. Is that 512MBs or 512KBs?

Thanks

On Thu, 2002-11-14 at 09:56, Bruce Momjian wrote:
> Usually vmstat shows page ins.  I also write a paper on this:
>
>     http://techdocs.postgresql.org/redir.php?link=http://www.ca.postgresql.org/docs/momjian/hw_performance/
>
> The techdocs site has other stuff, see "Optimzation" section:
>
>     http://techdocs.postgresql.org/
>
> ---------------------------------------------------------------------------
>
> 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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> >
--
Wei Weng
Network Software Engineer
KenCast Inc.