[Fwd: Interesting analysis of linux kernel threading by IBM]

From: Duane Hanf (hanfactuarial@uswest.net)
Date: Fri Jan 21 2000 - 12:14:43 EST

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    attached mail follows:


    Hi Werner,

    Thursday, January 20, 2000 7:11 PM
    Werner Almesberger <almesber@lrc.di.epfl.ch> wrote :
    > Maybe you should give examples of the overall performance for typical
    > CPU/memory bound loads for the extreme cases. I don't think many
    > people have a good intuition for how much CPU time their system
    > actually burns in the scheduler. E.g. -15% overall performance sounds
    > scary, while -15% on of whatever, say, an MP3 player and a simulation
    > may leave to the scheduler would be difficult to measure, let alone
    > notice.
    >
    > Also, please be sure to make the distinction between concurrently
    > running (i.e. on different CPUs), runnable (i.e. wanting to run), and
    > other processes (i.e. waiting for something else to happen) very
    > clear. Best if you mention all three categories in each example.

    I'm speaking about scheduling times that, as You can see inside the
    IBM guys ( Ray Bryant and Bill Hartner ) article
    http://www-4.ibm.com/software/developer/library/java2/index.html
    waste a great percent of CPU time under high workload, due to the fact that
    the actual scheduler linear scan the runqueue to find the best task to run.
    My approach gives a logarithmic response versus the linear of the current.
    My test suite is poor and is for this reason that I like if someone having a
    best
    testing console ( like IBM guys and others I hope ) gives a test to the
    patch.
    My Jun99 patch also includes a semaphore wake_up() rewrite that instead
    releasing all the N processes waiting in the queue for reschedule N-1 of
    them,
    it find the best task to release inside the wake_up() function.
    This patch avoid the peak of N processes flushed into the scheduler.
    Think about processes waiting for a connection into a socket for example.

    This patch is for 2.3.5.

    Cheers,
        Davide.



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