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SubjectRe: New Feature Idea: Compress swap file
Pavel Machek writes:
> Hi!
>
> > What all you folks seem to forget is that _seek_ time
> > is, by far, the dominant factor in swapping.
> >
> > Let's assume a 2MB/second, 9ms seek, 5400RPM disk.
> > With a disk like this, is takes 9 + (60000 (ms/min) / 5400) / 2 =
> > 14.5 ms to find a certain position on the disk.
> > And it takes 2meg/4k = 1/512th = 2ms to transfer the block.
> >
> > This means that we won't get a performance increase from
> > compressed swapping.
> >
> > Clustered swapping however, _is_ going to make a _huge_
> > difference. So if you want performance, better focus on
> > something that will work.
>
> Sorry, what is clustered swapping? Unless you have dedicated disc for
> swap (you don't have it, in most cases), you'll fight with normal fs
> for disc head. I'm not sure that anything clever will help.

If you can only afford one drive, sure. If you have two drives, there
is simply no excuse for not putting swap on a different disc than your
data. I've measured speed improvements of 2.5 to 3 times when the swap
partition is on a differnt disc than my data. This was for a dataset
about 30 MBytes on a machine with 64 MBytes of RAM.

Regards,

Richard....

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