Mailinglist Archive: opensuse (3666 mails)

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Re: [SLE] Maximum Swap Size
  • From: Paul Hewlett <hewlett@xxxxxxxxxxxxxxx>
  • Date: Tue, 8 Mar 2005 09:44:44 +0200
  • Message-id: <200503080944.44060.hewlett@xxxxxxxxxxxxxxx>
On Monday 07 March 2005 17:12, James Knott wrote:
> Bruce Marshall wrote:
> > On Sunday 06 March 2005 09:17 pm, John Sowden wrote:
> >>Actually, I thought this was a great question that only one person came
> >>close to answering. Is there a defined set of tradeoffs when expanding
> >> the swap size, in relation to RAM, taking into consideration CPU speed
> >> and possibly other variables that I am not aware of. If, instead of
> >> using the 2X rule for sizing a swap partition, we went to a 4X or 6X
> >> size, would the paging overhead not justify the expanded swap size, in
> >> terms of increasing performance?
> >
> > The best swap area you can have is one that doesn't get used. The size
> > of the swap area should be immaterial as long as it is large enough to
> > handle all of the swap. But if you are swapping a lot, you should look
> > elsewhere for performance gains. (as in increasing your RAM...)
> One situation I had in mind, was processing huge data files, so large
> that you wouldn't want to pay for all that RAM. Is processing it in
> memory space easier than doing the file I/O, to process it in chunks?

USually applications that access large files use memory-mapping via the mmap()
call. The mmap() call converts an open file into a pseudo memory area.
Accessing this memory area causes the kernel to do the necessary file I/O
transparently. SGI had a whole host of video processing applications that
used this technique.

Regards Paul

Paul Hewlett (Linux #359543) Email:`echo az.oc.evitcaten@ttelweh | rev`
Tel: +27 21 852 8812 Cel: +27 72 719 2725 Fax: +27 86 672 0563

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