Messages in this thread | | | Date | Wed, 29 Apr 2009 12:24:09 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH] sched: account system time properly |
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* Martin Schwidefsky <schwidefsky@de.ibm.com> wrote:
> On Wed, 29 Apr 2009 11:20:03 +0200 > Eric Dumazet <dada1@cosmosbay.com> wrote: > > > 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 > > Very good. Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Thanks.
Eric, mind (re-)sending the patch with Martin's ack included, and with either a suitable impact-line footer or an extra paragraph that describes the bug you found (and how it shows up in practice) and how the patch fixed that problem.
Thanks,
Ingo -- 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/
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