| From: | "Shridhar Daithankar" <shridhar_daithankar(at)persistent(dot)co(dot)in> |
|---|---|
| To: | pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: swapping? |
| Date: | 2002-11-14 14:37:24 |
| Message-ID: | 3DD4027C.4503.18465B@localhost |
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| Lists: | pgsql-performance |
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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