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Date: Thu, 19 Jul 2007 18:16:43 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Andrew Morton <akpm@linux-foundation.org>, linux-kernel@vger.kernel.org,
       Linus Torvalds <torvalds@linux-foundation.org>, stable@kernel.org,
       Greg KH <greg@kroah.com>, Chris Wright <chrisw@sous-sol.org>,
       Jens Axboe <jens.axboe@oracle.com>,
       Srivatsa Vaddagiri <vatsa@in.ibm.com>,
       Jan Glauber <jang@linux.vnet.ibm.com>, Andi Kleen <ak@suse.de>
Subject: Re: [patch] sched: implement cpu_clock(cpu) high-speed time
	source, take #2
Message-ID: <20070719161643.GA5153@elte.hu>
References: <469F75AF.5080000@goop.org> <20070719143528.GA8278@elte.hu> <469F793E.6030006@goop.org> <20070719145058.GA11971@elte.hu> <469F7D7A.204@goop.org> <20070719150955.GA19373@elte.hu> <469F8179.2060802@goop.org> <20070719154254.GA24225@elte.hu> <20070719154449.GA28998@elte.hu> <469F8D28.1010304@goop.org>
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* Jeremy Fitzhardinge <jeremy@goop.org> wrote:

> > how about the patch below instead? (which, unlike the first one, 
> > happens to build and boot ;-)
> 
> Yes, that should be fine if its just based on sched_clock.  Presumably 
> that means that any architecture (eg, s390) which chooses to implement 
> sched_clock as unstolen time will get good behaviour from softlockup 
> as well as the scheduler.

yeah, that's the idea.

> How does this interact with the sched_clock changes Andi just posted?

those changes pose no problem, and they are largely orthogonal. Andi's 
changes should improve the quality of sched_clock() on some boxes that 
encounter a cpu frequency transition that makes the TSC readout 
unreliable.

	Ingo