From: Christian Borntraeger <borntraeger@de.ibm.com>
To: schwidefsky@de.ibm.com
Subject: Re: [accounting regression since rc1]  scheduler updates
Date: Tue, 21 Aug 2007 09:00:54 +0200
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Cc: Ingo Molnar <mingo@elte.hu>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Andrew Morton <akpm@linux-foundation.org>, linux-kernel@vger.kernel.org,
       Jan Glauber <jang@linux.vnet.ibm.com>, heiko.carstens@de.ibm.com,
       Paul Mackerras <paulus@samba.org>
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Am Montag, 20. August 2007 schrieb Martin Schwidefsky:
> On Mon, 2007-08-20 at 20:08 +0200, Ingo Molnar wrote:
> 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.
> 
> > If a virtual CPU is idle then i think the "real = steal, virtual = 0" 
> > way of thinking about idle looks a bit unnatural to me - wouldnt it be 
> > better to think in terms of "steal = 0, virtual = real" ? Basically a 
> > virtual CPU can idle at "perfect speed", without the host "stealing" any 
> > cycles from it. And with that way of thinking, if s390 passed in the 
> > real-idle-time value to the new callbacks below it would all fall into 
> > place. Hm?

Martin,

I think we already do something like this. If you look at cpustat in 2.6.22 
and earlier we already have steal increase = 0, idle increase = 100 % on an 
idle cpu, even on s390. So while from the hardware perspective steal is 
growing, we do the right thing in Linux, no?

Chrisian
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