linux-kernel - Re: Rescheduling interrupts

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Message-ID: <20080122152333.GB19590@elte.hu>
Date:	Tue, 22 Jan 2008 16:23:34 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	S.Çağlar Onur <caglar@...dus.org.tr>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Arjan van de Ven <arjan@...ux.intel.com>
Subject: Re: Rescheduling interrupts


* S.Çağlar Onur <caglar@...dus.org.tr> wrote:

> 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

thanks, these seem to be mostly normal wakeups from standard tasks:

 IPI from task kdm_greet:2118 on CPU#0:
 IPI from task X:2079 on CPU#1:
 IPI from task kdm_greet:2118 on CPU#0:
 IPI from task hald-addon-inpu:2009 on CPU#1:
 IPI from task events/0:7 on CPU#1:
 IPI from task bash:2129 on CPU#0:
 IPI from task kdm_greet:2118 on CPU#0:
 IPI from task events/0:7 on CPU#1:
 IPI from task events/0:7 on CPU#1:
 IPI from task events/0:7 on CPU#1:
 IPI from task bash:3902 on CPU#1:
 IPI from task bash:3902 on CPU#1:
 IPI from task amarokapp:3423 on CPU#1:
 IPI from task amarokapp:3423 on CPU#1:
 IPI from task amarokapp:3423 on CPU#1:
 IPI from task X:2079 on CPU#0:
 IPI from task yakuake:3422 on CPU#0:
 IPI from task X:2079 on CPU#1:
 IPI from task amarokapp:3423 on CPU#1:
 IPI from task amarokapp:3423 on CPU#1:

could you also add a similar IPI printouts (with the same panic_timeout 
logic) to arch/x86/kernel/smp_32.c's smp_reschedule_interrupt() function 
- while still keeping the other printouts too?

Could you also enable PRINTK_TIME timestamps, so that we can see the 
timings? (And do a "dmesg -n 1" so that the printks happen fast and the 
timings are accurate.) I'd suggest to increase CONFIG_LOG_BUF_SHIFT to 
20, so that your dmesg buffer is large enough. Plus try to capture 100 
events, ok?

My theory is that for whatever reason we get "repeat" IPIs: multiple 
reschedule IPIs although the other CPU only initiated one.

	Ingo
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