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

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Message-ID: <20151118160439.GE30184@e105550-lin.cambridge.arm.com>
Date:	Wed, 18 Nov 2015 16:04:40 +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 07:11:31AM -0800, Jacob Pan wrote:
> On Wed, 18 Nov 2015 15:09:44 +0000
> Morten Rasmussen <morten.rasmussen@....com> wrote:
> 
> > Okay. But it does mean that the defeault idle period is 5 ticks (50ms
> > @ HZ=100) and not 5 ms
> correct. my reason is to scale with various HZ values.

50ms seems quite long for embedded applications. OTOH, it has to be long
enough to enter a package idle state and stay there for a while. You
would surely notice it when it kicks in on an Android device.

Do you intend to use it only as a last option? One might want to keep
using inefficient frequencies (P-states) if those don't cause UI lag
then.
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