linux-kernel - Re: [RFC PATCH v2 3/3] sched: introduce synchronized idle injection

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Message-ID: <20151110145823.GD17308@twins.programming.kicks-ass.net>
Date:	Tue, 10 Nov 2015 15:58:23 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Jacob Pan <jacob.jun.pan@...ux.intel.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Rafael Wysocki <rafael.j.wysocki@...el.com>,
	Len Brown <len.brown@...el.com>,
	Andi Kleen <andi.kleen@...el.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Paul Turner <pjt@...gle.com>,
	Tim Chen <tim.c.chen@...ux.intel.com>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Eduardo Valentin <edubezval@...il.com>,
	Punit Agrawal <punit.agrawal@....com>,
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Subject: Re: [RFC PATCH v2 3/3] sched: introduce synchronized idle injection

On Tue, Nov 10, 2015 at 06:01:16AM -0800, Jacob Pan wrote:
> On Tue, 10 Nov 2015 14:23:24 +0100
> Peter Zijlstra <peterz@...radead.org> wrote:

> > It looks like what you want is:
> > 
> > 	hrtimer_forward(hrt, period);
> > 
> > unconditionally.

> In the ideal world yes. But my thinking was that timers may not be so
> accurate to deliver interrupts, over the time the timeout error may
> accumulate so that eventually timers will be out of sync.

Timers have a global time base. Even if individual deliveries have an
error, there is no accumulated error.

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