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    SubjectRe: Scheduler regression: Too frequent timer interrupts(?)
    On Fri, 17 Apr 2009, Peter Zijlstra wrote:

    > And a random 1us cutoff, is well, random.

    Its got to be somewhere.

    > If you want to reduce interrupts, that's fine, but not counting an
    > interrupt because its below the magic 1us marker sounds a bit, well,
    > magic -- might work for you, might not for me on another machine, might
    > even be compiler dependent.

    The point is to reduce the interrupts of user space application. Hardware
    interrupts etc are something else. Maybe I should not use the term
    interrupt. Cpu unavailability? Cache pollution?

    > So 5 <1us interruption are not at all accounted, whereas a single 1>us
    > interruption is. I'd rather get rid of those 5 than try and shave a bit
    > of the one, if you get what I mean.

    Ok. We can set the threshold lower and see how that goes.

    > Furthermore, yes the scheduler is one of those jiffy tick users, but
    > there are more. We can do ntp/gtod things in there, there is process
    > accounting, there is some RCU machinery, timers etc..

    Again things were fine before the scheduler changed.

    Could we defer interrupts if a single process is running on a cpu and
    there is no other process on the runqueue and no other use of the timer
    interrupt?



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