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Re: [PLUG] vmstat and swapping out pages; need more RAM?
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In the message dated: Mon, 15 May 2006 16:10:47 EDT,
The pithy ruminations from Jeff Abrahamson on
<Re: [PLUG] vmstat and swapping out pages; need more RAM?> were:
=>
=>
=> On Mon, May 15, 2006 at 03:59:01PM -0400, Douglas Muth wrote:
=> > It looks like there is a lot of swap space being used, even though
=> > you look okay on RAM.
=>
=> Remember that a good VM system will actually *use* swap space, though
=> what it uses it for is another question with a long answer on which
=> reasonable people might disagree. If you aren't using swap, you have
=> a bad VM system or you aren't do anything and have a tiny kernel.
Care to expand on that? I'm really interested in getting some more details.
I'd say that:
a good memory management system will actually *use* virtual memory
(where virtual memory = (RAM + swap))...if you aren't using [almost]
all of your RAM you aren't doing anything and have a tiny kernel.
However, if the VM is swapping processes to disk in order to use RAM for
anything other than running other processes (ie., for filesystem buffering),
I'd say it's not a well-behaved VM. If the VM is swapping processes to disk in
order to use RAM for running other processes, then you need more RAM.
=>
=> What's bad, though, is things going in and out of swap too often.
If you've got the capacity and $$ to expand RAM, then I define "swap too often"
as "swap at all".
My personal idea of a good balance: all the RAM is used, and swap space doesn't
get touched for 80+% of normal usage.
Mark "added a 4G swapfile to an SGI w. 8G of VM this afternoon" Bergman
=>
=> --=20
=> Jeff
=>
=> Jeff Abrahamson <http://jeff.purple.com/> +1 215/837-2287
=> GPG fingerprint: 1A1A BA95 D082 A558 A276 63C6 16BF 8C4C 0D1D AE4B
=>
-----
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