linux-kernel - Re: [PATCH 3/4] sched: introduce synchronized idle injection

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Message-ID: <20151118150944.GC30184@e105550-lin.cambridge.arm.com>
Date:	Wed, 18 Nov 2015 15:09:44 +0000
From:	Morten Rasmussen <morten.rasmussen@....com>
To:	Jacob Pan <jacob.jun.pan@...ux.intel.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>, Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	John Stultz <john.stultz@...aro.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
	Len Brown <len.brown@...el.com>,
	Rafael Wysocki <rafael.j.wysocki@...el.com>,
	Eduardo Valentin <edubezval@...il.com>,
	Paul Turner <pjt@...gle.com>
Subject: Re: [PATCH 3/4] sched: introduce synchronized idle injection

On Wed, Nov 18, 2015 at 06:52:33AM -0800, Jacob Pan wrote:
> On Wed, 18 Nov 2015 14:04:41 +0000
> Morten Rasmussen <morten.rasmussen@....com> wrote:
> 
> > Then I'm confused :-/
> > 
> > I see the hrtimers, but the actual idle duration appears to be in
> > ticks rather than ms and then converted later.
> > 
> > +/* Duration of idle time in ticks of each injection period
> > */ +unsigned int sysctl_sched_cfs_idle_inject_duration = 5UL;
> > 
> > ...and futher down we have:
> > 
> > +       duration_msec =
> > jiffies_to_msecs(sysctl_sched_cfs_idle_inject_duration);
> I used hrtimers but still round around tick boundaries of ktime.
> It is more reliable than jiffies in terms of getting timely updates.

Okay. But it does mean that the defeault idle period is 5 ticks (50ms @
HZ=100) and not 5 ms.
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