Re: Rescheduling interrupts

["Vegard Nossum" <vegard.nossum@gmail.com>]

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On Tue, May 13, 2008 at 8:03 PM, Vegard Nossum <vegard.nossum@gmail.com> wrote:> Hi,>>>  On Tue, Jan 22, 2008 at 6:05 PM, Ingo Molnar <mingo@elte.hu> wrote:>  >>  >  * S.Çağlar Onur <caglar@pardus.org.tr> wrote:>  >>  >>  > > > My theory is that for whatever reason we get "repeat" IPIs: multiple>  >  > > reschedule IPIs although the other CPU only initiated one.>  >  >>  >  > Ok, please see http://cekirdek.pardus.org.tr/~caglar/dmesg.3rd :)>  >>  >  hm, the IPI sending and receiving is nicely paired up:>  >>  >  [  625.795008] IPI (@smp_reschedule_interrupt) from task swapper:0 on CPU#1:>  >  [  625.795223] IPI (@native_smp_send_reschedule) from task amarokapp:2882 on CPU#1:>  >>  >  amarokapp does wake up threads every 20 microseconds - that could>  >  explain it. It's probably Xorg running on one core, amarokapp on the>  >  other core. That's already 100 reschedules/sec.>>  Was this IPI thing ever resolved/fixed? I'm seeing the exact same>  thing on my newest Fedora 8 kernel (2.6.24.5-85.fc8) now:>>   33.3% (334.0)      <kernel IPI> : Rescheduling interrupts>>  And I know for sure that this did not show up a couple of months back.>>  If the cause of this is known, please let me know about it. If it>  isn't, I will start a bisect run now :-)
Ok -- just a confirmation. I have this on v2.6.26-rc1:
Running only init=/bin/sh (from busybox) and powertop shows:kernel IPI : Rescheduling interrupts
completely idle box (except powertop): 1 wakeups/secone busy-loop[1]: 2 wakeups/sectwo busy-loops: 500 wakeups/sec
So it seems like a real bug to me.

Vegard
[1]: while true; do echo hi; done
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