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    SubjectRe: linux scheduler limitations?
    I'm using 2.4.2-ac26, but I've noticed the same behavior with all the 2.4
    kernels I've seen so far.

    I haven't even tried on 2.2

    - Fabio

    David Lang wrote:

    > 2.2 or 2.4 kernel?
    >
    > the 2.4 does a MUCH better job of dealing with large numbers of processes.
    >
    > David Lang
    >
    > On Thu, 29 Mar 2001, Fabio Riccardi wrote:
    >
    > > Date: Thu, 29 Mar 2001 13:19:05 -0800
    > > From: Fabio Riccardi <fabio@chromium.com>
    > > To: linux-kernel@vger.kernel.org
    > > Subject: linux scheduler limitations?
    > >
    > > Hello,
    > >
    > > I'm working on an enhanced version of Apache and I'm hitting my head
    > > against something I don't understand.
    > >
    > > I've found a (to me) unexplicable system behaviour when the number of
    > > Apache forked instances goes somewhere beyond 1050, the machine
    > > suddently slows down almost top a halt and becomes totally unresponsive,
    > > until I stop the test (SpecWeb).
    > >
    > > Profiling the kernel shows that the scheduler and the interrupt handler
    > > are taking most of the CPU time.
    > >
    > > I understand that there must be a limit to the number of processes that
    > > the scheduler can efficiently handle, but I would expect some sort of
    > > gradual performance degradation when increasing the number of tasks,
    > > instead I observe that by increasing Apache's MaxClient linit by as
    > > little as 10 can cause a sudden transition between smooth working with
    > > lots (30-40%) of CPU idle to a total lock-up.
    > >
    > > Moreover the max number of processes is not even constant. If I increase
    > > the server load gradually then I manage to have 1500 processes running
    > > with no problem, but if the transition is sharp (the SpecWeb case) than
    > > I end-up having a lock up.
    > >
    > > Anybody seen this before? Any clues?
    > >
    > > - Fabio
    > >
    > >
    > > -
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    > >

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