Memory upgrade and swap partition size

[Kjel Anderson]

Thanks for that information. That is certainly very helpful.

Kjel

On 9/26/06, Jon maddog Hall <maddog at li.org> wrote:
>
> Kjel,
>
> kjel.anderson at gmail.com said:
> > I am probably exposing my ignorance by asking this, but I have to
> remember:
> > there are no stupid questions, just stupid people.
>
> This is not a stupid question.  Increasing SWAP size on your disk will not
> generally
> improve performance.  SWAP size increases will allow you to run more
> programs
> simultaneously or programs with with larger datasets, but the things
> related to
> "SWAP" that will generally give you better PERFORMANCE are:
>
> o RAID striping of your SWAP partition
> o placement of SWAP on a seldom used disk spindle (same thing with /tmp
> and /usr/tmp)
> o allocation and placement of multiple swap partitions to minimize disk
> latencies
> o having more RAM (always more RAM)
> o Solid state SWAP devices
>
> SWAP is used in two instances:
>
>         o you have more data than you have RAM memory (text is paged out
> of the
>           text files, not out of SWAP)
>         o after a certain period of inactivity, processes are "swapped"
> out to SWAP
>           to make room for the more active processes
>
> These are general rules of thumb.
>
> If your SWAP is not large enough, you will get fairly obvious error
> messages telling
> you that you are in that situation.
>
> Disk space is cheap these days, and I normally have a gig of swap space
> on my notebook, along with the two gigs of memory I have.  I can not
> remember the
> last time I ran out of "swap" space, if ever.  On the other hand, if you
> are running
> a large server with a large database, you might indeed run out of "swap"
> at some time.
>
> There are tuning parameters inside of the kernel that control SWAP, when
> it takes over,
> how much RAM is reserved for things like buffer cache and other forms of
> memory
> management, but this is probably more than you want to know or fiddle
> with.....trust
> me.
>
> md
> --
> Jon "maddog" Hall
> Executive Director           Linux International(R)
> email: maddog at li.org         80 Amherst St.
> Voice: +1.603.672.4557       Amherst, N.H. 03031-3032 U.S.A.
> WWW: http://www.li.org
>
> Board Member: Uniforum Association
> Board Member Emeritus: USENIX Association (2000-2006)
>
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