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SubjectRe: Rescheduling interrupts
Date
Hi;

22 Oca 2008 Sal tarihinde, Ingo Molnar şunları yazmıştı:
> * S.Çağlar Onur <caglar@pardus.org.tr> wrote:
>
> > Top causes for wakeups:
> > 59,9% (238,4) <kernel IPI> : Rescheduling interrupts
> > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> > 14,7% ( 58,6) amarokapp : schedule_timeout (process_timeout)
>
> hm, would be nice to figure out what causes these IPIs. Could you stick
> something like this into arch/x86/kernel/smp_32.c's
> smp_send_reschedule() function [this is the function that generates the
> IPI]:
>
> static void native_smp_send_reschedule(int cpu)
> {
> WARN_ON(cpu_is_offline(cpu));
> send_IPI_mask(cpumask_of_cpu(cpu), RESCHEDULE_VECTOR);
> if (panic_timeout > 0) {
> panic_timeout--;
> printk("IPI from task %s:%d on CPU#%d:\n",
> current->comm, current->pid, cpu);
> dump_stack();
> }
> }
>
> NOTE: if you run an SMP kernel then first remove these two lines from
> kernel/printk.c:
>
> if (!oops_in_progress && waitqueue_active(&log_wait))
> wake_up_interruptible(&log_wait);
>
> otherwise you'll get lockups. (the IPI is sent while holding the
> runqueue lock, so the printks will lock up)
>
> then wait for the bad condition to occur on your system and generate a
> stream of ~10 backtraces, via:
>
> echo 10 > /proc/sys/kernel/panic
>
> you should be getting 10 immediate backtraces - please send them to us.
> The backtraces should show the place that generates the wakeups. [turn
> on CONFIG_FRAME_POINTERS=y to get high quality backtraces.]
>
> If you do _not_ get 10 immediate backtraces, then something in the
> system is generating such IPIs outside of the scheduler's control. That
> would suggest some other sort of borkage.
>
> Ingo

I grabbed the logs two times to make sure to catch needed info. 1st [1] one is generated while "Rescheduling interrupts" wakeups ~200 times and 2nd one generated for ~350 wakeups.

[1] http://cekirdek.pardus.org.tr/~caglar/dmesg.1st
[2] http://cekirdek.pardus.org.tr/~caglar/dmesg.2nd

Cheers
--
S.Çağlar Onur <caglar@pardus.org.tr>
http://cekirdek.pardus.org.tr/~caglar/

Linux is like living in a teepee. No Windows, no Gates and an Apache in house!
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