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    SubjectRe: Network slowdown due to CFS

    * Jarek Poplawski <> wrote:

    > > firstly, there's no notion of "timeslices" in CFS. (in CFS tasks
    > > "earn" a right to the CPU, and that "right" is not sliced in the
    > > traditional sense) But we tried a conceptually similar thing [...]
    > >From kernel/sched_fair.c:
    > "/*
    > * Targeted preemption latency for CPU-bound tasks:
    > * (default: 20ms, units: nanoseconds)
    > *
    > * NOTE: this latency value is not the same as the concept of
    > * 'timeslice length' - timeslices in CFS are of variable length.
    > * (to see the precise effective timeslice length of your workload,
    > * run vmstat and monitor the context-switches field)
    > ..."
    > So, no notion of something, which are(!) of variable length, and which
    > precise effective timeslice lenght can be seen in nanoseconds? (But
    > not timeslice!)

    You should really read and understand the code you are arguing about :-/

    In the 2.6.22 scheduler, there was a p->time_slice per task variable
    that could be manipulated. (Note, in 2.6.22's sched_yield() did not
    manipulate p->time_slice.)

    sysctl_sched_latency on the other hand is not something that is per task
    (it is global) so there is no pending timeslice to be "cleared" as it
    has been suggested naively.

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      Last update: 2007-10-03 10:19    [W:0.022 / U:30.992 seconds]
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