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    SubjectRe: Subtle MM bug
    On 17 Jan 2001, Zlatko Calusic wrote:
    > Rik van Riel <riel@conectiva.com.br> writes:
    >
    > > > Second test: kernel compile make -j32 (empirically this puts the
    > > > VM under load, but not excessively!)
    > > >
    > > > 2.2.17 -> make -j32 392.49s user 47.87s system 168% cpu 4:21.13 total
    > > > 2.4.0 -> make -j32 389.59s user 31.29s system 182% cpu 3:50.24 total
    > > >
    > > > Now, is this great news or what, 2.4.0 is definitely faster.
    > >
    > > One problem is that these tasks may be waiting on kswapd when
    > > kswapd might not get scheduled in on time. On the one hand this
    > > will mean lower load and less thrashing, on the other hand it
    > > means more IO wait.
    >
    > Hm, if all tasks are waiting for memory, what is stopping kswapd
    > to run? :)

    Suppose you have 8 high-priority tasks waiting on kswapd
    and one lower-priority (but still higher than kswapd)
    process running and preventing kswapd from doing its work.
    Oh .. and also preventing the higher-priority tasks from
    being woken up and continuing...


    Rik
    --
    Virtual memory is like a game you can't win;
    However, without VM there's truly nothing to lose...

    http://www.surriel.com/
    http://www.conectiva.com/ http://distro.conectiva.com.br/

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