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SubjectRe: VM performance

On Wed, 27 Jan 1999 22:37:56 +0200, Nimrod Zimerman
<> said:

> The fact that the kernel trims the cache doesn't mean swap isn't used
> needlessly. The cache behavior is still much worse than it used to be
> (though in 2.2.0, it has greatly improved pre9's behavior).

Do you have performance timings to back this up? I'd like to see them.

> It isn't fine, not at all. If you want, I can supply some vmstat reports to
> show what I mean.

Fine, but vmstat alone means nothing in this respect, because the VM can
play a number of cunning tricks to keep the same swap page both on disk
and in memory. A large swap usage in vmstat doesn't tell us anything
about how fast things are moving. Wall clock time is the only reliable
benchmark here.

vmstat is _very_ useful at identifying why you see the observed
performance, but I won't accept that just because vmstat doesn't say
what it used to that the VM must be doing worse!


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