linux-kernel - Re: [NOHZ] Remove scheduler_tick_max

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Message-ID: <20141110153147.GK4901@linux.vnet.ibm.com>
Date:	Mon, 10 Nov 2014 07:31:47 -0800
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	Christoph Lameter <cl@...ux.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Gilad Ben-Yossef <gilad@...yossef.com>,
	Tejun Heo <tj@...nel.org>,
	John Stultz <john.stultz@...aro.org>,
	Mike Frysinger <vapier@...too.org>,
	Minchan Kim <minchan.kim@...il.com>,
	Hakan Akkan <hakanakkan@...il.com>,
	Max Krasnyansky <maxk@....qualcomm.com>,
	Hugh Dickins <hughd@...gle.com>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [NOHZ] Remove scheduler_tick_max_deferment

On Mon, Nov 10, 2014 at 12:41:38PM +0530, Viresh Kumar wrote:
> On 6 November 2014 22:54, Christoph Lameter <cl@...ux.com> wrote:
> 
> > We did not need to housekeeper in the dynticks idle case. What is so
> > different about dynticks busy?
> 
> We do have a running task here and so the stats are important..
> 
> > I may not have the complete picture of the timer tick processing in my
> > mind these days (it has been a lots of years since I did any work there
> > after all) but as far as my arguably simplistic reading of the code goes I
> > do not see why a housekeeper would be needed there. The load is constant
> > and known in the dynticks busy case as it is in the dynticks idle case.
> 
> I tried to initiate a thread on similar stuff, might be helpful:
> 
> https://lkml.org/lkml/2014/5/22/131

Would it make sense for unlimited max deferment to be available as
a boot parameter?  That would allow people who want tick-free execution
more than accurate stats to get that easily, while keeping stats accurate
for everyone else.

							Thanx, Paul

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