linux-kernel - Re: fast path cycle muncher (vmstat: make vmstat_updater deferrable again and shut down on idle)

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Message-ID: <1453828136.3534.9.camel@gmail.com>
Date:	Tue, 26 Jan 2016 18:08:56 +0100
From:	Mike Galbraith <umgwanakikbuti@...il.com>
To:	Christoph Lameter <cl@...ux.com>
Cc:	Michal Hocko <mhocko@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: fast path cycle muncher (vmstat: make vmstat_updater deferrable
 again and shut down on idle)

On Tue, 2016-01-26 at 10:26 -0600, Christoph Lameter wrote:
> On Tue, 26 Jan 2016, Mike Galbraith wrote:
> 
> > > Why would the deferring cause this overhead?
> > 
> > Because we schedule to idle cores aggressively, thus we may pop in and
> > out of idle at high frequency.
> 
> Whats the point of going idle if you have things to do soon?

When a task schedules off, how do you know it'll be back at all, much
less soon?

	-Mike