linux-kernel - Re: 2.6.24-rc6-git12: Reported regressions from 2.6.23

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Date:	Sun, 6 Jan 2008 10:55:01 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Mark Lord <lkml@....ca>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Adrian Bunk <bunk@...nel.org>
Subject: Re: 2.6.24-rc6-git12: Reported regressions from 2.6.23


* Mark Lord <lkml@....ca> wrote:

> Rafael J. Wysocki wrote:
>> This message contains a list of some regressions from 2.6.23 reported since
>> 2.6.24-rc1 was released, for which there are no fixes in the mainline I know
>> of.  If any of them have been fixed already, please let me know.
> ..
>> Subject		: 20000+ wake-ups/second in 2.6.24
>> Submitter	: Mark Lord <lkml@....ca>
>> Date		: 2007-12-02 04:23
>> References	: http://lkml.org/lkml/2007/12/1/141
>> 		  http://bugzilla.kernel.org/show_bug.cgi?id=9489
>> Handled-By	: Arjan van de Ven <arjan@...radead.org>
>>
> ..
>
> I have only seen that one once, and I think it was Arjan who said that 
> it has been observed rarely by other people as well. The bugzilla 
> entry is mostly just to track the darned thing, but it seems unlikely 
> that anyone will find/fix it for 2.6.24. No big deal, but it would be 
> good to have somebody knowledgeable in clocks/interrupts try and track 
> it down.
>
> I wonder if it's just a babbling IRQ on resume, before the driver has 
> run it's resume code or something ?

i've read the discussions, and i cannot see it analyzed anywhere _what_ 
causes the wakeups. And how are these wakeups counted? Is this based on 
powertop output:

 Wakeups-from-idle per second : 20.4     interval: 1.8s

? Somewhere i saw it mentioned that "the CPU throws out of C mode". What 
does that mean - does it mean we try to idle again and again, but we 
immediately return from C mode - while this all looks like "idle" time 
to the scheduler (so 'top' will show lots of idle time), but the ACPI 
wakeup counters are going up like mad? What is /proc/interrupts doing 
when this happens - is any of the irq sources going upwards?

	Ingo
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