lkml.org 
[lkml]   [2005]   [Jan]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH]sched: Isochronous class v2 for unprivileged soft rt scheduling
    utz lehmann wrote:
    > @@ -2406,6 +2489,10 @@ void scheduler_tick(void)
    > task_t *p = current;
    >
    > rq->timestamp_last_tick = sched_clock();
    > + if (iso_task(p) && !rq->iso_refractory)
    > + inc_iso_ticks(rq, p);
    > + else
    > + dec_iso_ticks(rq, p);
    >
    > scheduler_tick() is not only called by the timer interrupt but also form
    > the fork code. Is this intended? I think the accounting for

    The calling from fork code only occurs if there is one millisecond of
    time_slice left so it will only very rarely be hit. I dont think this
    accounting problem is worth worrying about.

    > iso_refractory is wrong. Isn't calling it from
    > timer.c::update_process_times() better?
    >
    > And shouldn't real RT task also counted? If RT tasks use 40% cpu you can
    > lockup the system as unprivileged user with SCHED_ISO because it doesn't
    > reach the 70% cpu limit.

    Ah yes. Good point. Will add that to the equation.

    > Futher on i see a fundamental problem with this accounting for
    > iso_refractory. What if i manage as unprivileged user to run a SCHED_ISO
    > task which consumes all cpu and only sleeps very short during the timer
    > interrupt? I think this will nearly lockup or very slow down the system.
    > The iso_cpu limit can't guaranteed.

    Right you are. The cpu accounting uses primitive on-interrupt run time
    which as we know is not infallible. To extend this I'll have to keep a
    timer based on the sched_clock which is already implemented. That's
    something for me to work on.

    > sysrq-n causes a reboot.

    And that will need looking into.

    Thanks very much for your comments!

    Cheers,
    Con
    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2005-03-22 14:09    [W:0.024 / U:31.576 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site