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    SubjectRe: Linux scheduler, overscheduling performance, threads
    I've given this thread up.  While I'm not convinced that there isn't a
    problem, I am convinced that most people on this list are convinced that
    there isn't. When/if it bites me, I'll write a patch and have real code
    to show people. If it bites IBM before it bites me and they fix it, well
    and good. So in a sense it isn't a problem- if it becomes one it can (and
    will) get fixed.

    On Mon, 24 Jan 2000, Ingo Molnar wrote:

    >
    > On Thu, 20 Jan 2000, Brian Hurt wrote:
    >
    > > Following this thread off and on since it's inception, and being a Java
    > > programmer myself, can I offer some observations?
    > >
    > > Thousands of threads in a program is not unreasonable. If you may want to
    > > take full advantage of a 128 CPU machine, for example, you need _at_
    > > _least_ 128 threads. If your threads spend most of their time blocking,
    > > you need even more threads, you need to overschedule, to make sure you
    > > generally have enough threads not blocking to make sure CPUs aren't going
    > > to waste. Unfortunately, due to vagaries of the system, you will have
    > > points when most of the threads become runnable at once.
    >
    > i believe you are confusing '2000 threads created and happily waiting
    > blocked to do something' and the '2000 threads running' case. I
    > specifically included a quick benchmark showing 20 thousand threads being
    > around on my system and not impacting Linux scheduler performance the
    > slightest. What i say is that more than nr_cpus*2 _running_ (ie. currently
    > waiting for the CPU, not some other resource) threads are bad.
    >
    > -- mingo
    >
    >


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