linux-kernel - Re: [accounting regression since rc1] scheduler updates

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Message-ID: <20070820190509.GA3714@elte.hu>
Date:	Mon, 20 Aug 2007 21:05:09 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Martin Schwidefsky <schwidefsky@...ibm.com>
Cc:	Christian Borntraeger <borntraeger@...ibm.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Jan Glauber <jang@...ux.vnet.ibm.com>,
	heiko.carstens@...ibm.com, Paul Mackerras <paulus@...ba.org>
Subject: Re: [accounting regression since rc1]  scheduler updates


* Martin Schwidefsky <schwidefsky@...ibm.com> wrote:

> On Mon, 2007-08-20 at 20:08 +0200, Ingo Molnar wrote:
> > For sched_clock()'s behavior while the virtual CPU is idle: my current 
> > idea for that is the patch below (a loosely analoguous problem exists 
> > with nohz/dynticks): it makes sched_clock() valid across idle periods 
> > too and uses wall-clock time for that.
> 
> Ok, that would mean that sched_clock can just return the virtual cpu 
> time and the two hooks starts and stops the idle periods as far as the 
> scheduler is concerned. In this case we can use the patch from Jan 
> with the new implementation for sched_clock and add the two hooks to 
> the places where the cpu-idle notifiers are done (do_monitor_call and 
> default_idle). In fact this could be an idle-notifier. Hmm, I take a 
> closer look tomorrow when I'm back at the office.

ok. Just to make it sure wrt. release-management: you said s390 
sched_clock() is currently at least as precise as stime/utime - so this 
would suggest that there is no regression over v2.6.22? Regardless of 
whether it's a live regression or not, i think we want the nohz 
improvement (and the s390 patch if the callbacks are OK to you) in .23, 
and we want to migrate all users of "raw" sched_clock() [blktrace, 
softlockup-detector, print-timestamps, etc.] over to the better 
cpu_clock() interface.

	Ingo
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