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

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Message-ID: <20151118061026.03a28616@yairi>
Date:	Wed, 18 Nov 2015 06:10:26 -0800
From:	Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Peter Zijlstra <peterz@...radead.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>, jacob.jun.pan@...ux.intel.com
Subject: Re: [PATCH 3/4] sched: introduce synchronized idle injection

On Wed, 18 Nov 2015 09:36:22 +0100
Ingo Molnar <mingo@...nel.org> wrote:

> > 
> > This patch introduces a scheduler based idle injection method, it
> > works by blocking CFS runqueue synchronously and periodically. The
> > actions on all online CPUs are orchestrated by per CPU hrtimers.
> > 
> > Two sysctl knobs are given to the userspace for selecting the
> > percentage of idle time as well as the forced idle duration for each
> > idle period injected.  
> 
> What's the purpose of these knobs? Just testing, or will some
> user-space daemon set them dynamically?
> 
yes, it is to be used by userspace daemon such as thermal daemon.
Though there are interests from in kernel thermal governor but that is
another story.

> I also think that naming it 'idle injection' is pretty euphemistic:
> this is forced idling, right? So why not name it CFS_FORCED_IDLE?
yes, it is forced idle. sounds good.
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