linux-kernel - Re: Rescheduling interrupts

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Message-ID: <19f34abd0805131103q136e28ddg359de5822b401e0c@mail.gmail.com>
Date:	Tue, 13 May 2008 20:03:06 +0200
From:	"Vegard Nossum" <vegard.nossum@...il.com>
To:	"Ingo Molnar" <mingo@...e.hu>
Cc:	"S.Çağlar Onur" <caglar@...dus.org.tr>,
	LKML <linux-kernel@...r.kernel.org>,
	"Arjan van de Ven" <arjan@...ux.intel.com>
Subject: Re: Rescheduling interrupts

Hi,

On Tue, Jan 22, 2008 at 6:05 PM, Ingo Molnar <mingo@...e.hu> wrote:
>
>  * S.Çağlar Onur <caglar@...dus.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 :-)

Thanks.


Vegard

-- 
"The animistic metaphor of the bug that maliciously sneaked in while
the programmer was not looking is intellectually dishonest as it
disguises that the error is the programmer's own creation."
	-- E. W. Dijkstra, EWD1036