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    SubjectRe: [PATCH] sched: account system time properly
    Martin Schwidefsky a écrit :
    > On Wed, 29 Apr 2009 09:46:17 +0200
    > Eric Dumazet <dada1@cosmosbay.com> wrote:
    >
    >> Eric Dumazet a écrit :
    >>> Andrew Morton a écrit :
    >>>
    >>> So, if IRQs are interrupting idle task, I guess if (p != rq->idle) will be false.
    >>>
    >
    > If an IRQ interrupts the idle task the tick is supposed to be accounted
    > as an idle tick. Only if the IRQ interrupted the system while it has
    > been in hardirq or softirq processing then it should be accounted as
    > system tick.
    >
    >> Maybe following patch is needed ?
    >>
    >> [PATCH] sched: account system time properly
    >>
    >> When idle task is interrupted by an IRQ, time accounting considers CPU is idle,
    >> even while it should account for hard or softirq.
    >>
    >> Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
    >>
    >> diff --git a/kernel/sched.c b/kernel/sched.c
    >> index b902e58..26efa47 100644
    >> --- a/kernel/sched.c
    >> +++ b/kernel/sched.c
    >> @@ -4732,7 +4732,7 @@ void account_process_tick(struct task_struct *p, int user_tick)
    >>
    >> if (user_tick)
    >> account_user_time(p, one_jiffy, one_jiffy_scaled);
    >> - else if (p != rq->idle)
    >> + else if ((p != rq->idle) || (irq_count() != HARDIRQ_OFFSET))
    >> account_system_time(p, HARDIRQ_OFFSET, one_jiffy,
    >> one_jiffy_scaled);
    >> else
    >
    > That patch makes a lot of sense to me. Does it fix the problem?
    >

    Yes it does, on my machine at least :

    11:18:48 AM CPU %usr %nice %sys %iowait %irq %soft %steal %guest %idle
    11:18:58 AM all 0.00 0.00 0.00 0.00 0.21 0.69 0.00 0.00 99.10
    11:18:58 AM 0 0.00 0.00 0.00 0.00 1.70 5.50 0.00 0.00 92.80 << HERE >>
    11:18:58 AM 1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 100.00
    11:18:58 AM 2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 100.00
    11:18:58 AM 3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 100.00
    11:18:58 AM 4 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 100.00
    11:18:58 AM 5 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 100.00
    11:18:58 AM 6 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 100.00
    11:18:58 AM 7 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 100.00



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