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

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Date:	Thu, 5 Nov 2015 11:27:32 -0800
From:	Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	Paul Turner <pjt@...gle.com>, Len Brown <len.brown@...el.com>,
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
	Tim Chen <tim.c.chen@...ux.intel.com>,
	Andi Kleen <andi.kleen@...el.com>,
	Rafael Wysocki <rafael.j.wysocki@...el.com>,
	jacob.jun.pan@...ux.intel.com
Subject: Re: [RFC PATCH 3/3] sched: introduce synchronized idle injection

On Thu, 5 Nov 2015 11:09:22 +0100
Peter Zijlstra <peterz@...radead.org> wrote:

> > Before:
> > CPU0 ______||| ||  |___________| || || |_____
> > CPU1 _________||| ||  |_______| || |_______
> > 
> > After:
> > 
> > CPU0 ______||| ||  |___________| || || |_____
> > CPU1 ______||| ||  |___________| || |_______
> > 
> > The goal is to have overlapping idle time if the load is already
> > balanced. The energy saving can be significant.  
> 
> I can see such a scheme having a fairly big impact on latency, esp.
> with forced idleness such as this. That's not going to be popular for
> many workloads.
agreed, it would be for limited workload. the key is to identify such
workloads at runtime. I am thinking to use the load average of
the busiest CPU as reference for consolidation, will not go beyond
that.
For the patch I have today and if you play a game like this one
http://www.agame.com/game/cut-the-rope
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