Messages in this thread | | | Date | Thu, 28 Jan 1999 18:16:35 GMT | From | "Stephen C. Tweedie" <> | Subject | Re: VM performance |
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Hi,
On Wed, 27 Jan 1999 22:37:56 +0200, Nimrod Zimerman <zimerman@deskmail.com> 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!
--Stephen
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