linux-kernel - Re: [patch] sched: implement cpu_clock(cpu) high-speed time source, take #2

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Date:	Thu, 19 Jul 2007 18:16:43 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	stable@...nel.org, Greg KH <greg@...ah.com>,
	Chris Wright <chrisw@...s-sol.org>,
	Jens Axboe <jens.axboe@...cle.com>,
	Srivatsa Vaddagiri <vatsa@...ibm.com>,
	Jan Glauber <jang@...ux.vnet.ibm.com>, Andi Kleen <ak@...e.de>
Subject: Re: [patch] sched: implement cpu_clock(cpu) high-speed time
	source, take #2


* Jeremy Fitzhardinge <jeremy@...p.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
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