linux-kernel - Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods

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Date:   Wed, 12 Jul 2017 14:22:49 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:     Frederic Weisbecker <fweisbec@...il.com>,
        Christoph Lameter <cl@...ux.com>,
        "Li, Aubrey" <aubrey.li@...ux.intel.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Aubrey Li <aubrey.li@...el.com>, tglx@...utronix.de,
        len.brown@...el.com, rjw@...ysocki.net, tim.c.chen@...ux.intel.com,
        arjan@...ux.intel.com, yang.zhang.wz@...il.com, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods

On Tue, Jul 11, 2017 at 11:09:31AM -0700, Paul E. McKenney wrote:
> On Tue, Jul 11, 2017 at 06:34:22PM +0200, Peter Zijlstra wrote:
> > Also, RCU_FAST_NO_HZ will make a fairly large difference here.. Paul
> > what's the state of that thing, do we actually want that or not?
> 
> If you are battery powered and don't have tight real-time latency
> constraints, you want it -- it has represent a 30-40% boost in battery
> lifetime for some low-utilization battery-powered devices.  Otherwise,
> probably not.

Would it make sense to hook that off of tick_nohz_idle_enter(); in
specific the part where we actually stop the tick; instead of every
idle?