Date: Thu, 5 Nov 2015 11:32:35 -0800
From: Jacob Pan <jacob.jun.pan@linux.intel.com>
To: Jacob Pan <jacob.jun.pan@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        LKML <linux-kernel@vger.kernel.org>,
        Arjan van de Ven <arjan@linux.intel.com>, Paul Turner <pjt@google.com>,
        Len Brown <len.brown@intel.com>,
        Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
        Tim Chen <tim.c.chen@linux.intel.com>,
        Andi Kleen <andi.kleen@intel.com>,
        Rafael Wysocki <rafael.j.wysocki@intel.com>
Subject: Re: [RFC PATCH 3/3] sched: introduce synchronized idle injection
Message-ID: <20151105113235.1b98d79c@icelake>
In-Reply-To: <20151105112732.7f600ba8@icelake>
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On Thu, 5 Nov 2015 11:27:32 -0800
Jacob Pan <jacob.jun.pan@linux.intel.com> wrote:

> On Thu, 5 Nov 2015 11:09:22 +0100
> Peter Zijlstra <peterz@infradead.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
sorry, hit the wrong button before finishing the email.
and set duration to 5, and 20% idle, it does not affect user experience
much. It saves ~15% power on my BDW ultrabook. Other unbalanced
workload such as video playback don't benefit, should be avoided.
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