linux-kernel - Re: Stolen and degraded time and schedulers

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Date:	Fri, 16 Mar 2007 09:38:28 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	Dan Hecht <dhecht@...are.com>, dwalker@...sta.com,
	cpufreq@...ts.linux.org.uk,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Con Kolivas <kernel@...ivas.org>,
	Chris Wright <chrisw@...s-sol.org>,
	Virtualization Mailing List <virtualization@...ts.osdl.org>,
	john stultz <johnstul@...ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>, paulus@...ibm.com,
	schwidefsky@...ibm.com, Rik van Riel <riel@...hat.com>
Subject: Re: Stolen and degraded time and schedulers


* Jeremy Fitzhardinge <jeremy@...p.org> wrote:

> Ingo Molnar wrote:
> > touching the 'timer tick' is the wrong approach. 'stolen time' only 
> > matters to the /scheduler tick/. So extend the hypervisor interface to 
> > allow the injection of 'virtual' scheduler tick events: via the use of a 
> > special clockevents device - do not change clockevents itself.
> 
> I didn't.  I was using sloppy terminology: I hang the stolen time 
> accounting off the Xen timer interrupt routine, just so that it gets 
> run every now and again.

i dont understand: how are you separating 'stolen time' drifts from 
events generated for absolute timeouts?

> I suppose I could explicitly hook stolen time accounting into the 
> scheduler, but its not obvious to me that it's necessary.

right now i dont see any clean way to solve this problem without having 
two clockevents drivers: one for the scheduler, one for timer events.

	Ingo
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