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

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Message-ID: <alpine.DEB.2.20.1601261218500.1909@east.gentwo.org>
Date:	Tue, 26 Jan 2016 12:19:20 -0600 (CST)
From:	Christoph Lameter <cl@...ux.com>
To:	Mike Galbraith <umgwanakikbuti@...il.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, 26 Jan 2016, Mike Galbraith wrote:

> On Tue, 2016-01-26 at 10:26 -0600, Christoph Lameter wrote:
> > On Tue, 26 Jan 2016, Mike Galbraith wrote:
> >
> > > On Tue, 2016-01-26 at 03:14 +0100, Mike Galbraith wrote:
> > >
> > > > Perf and RT say we don't want quiet_vmstat() in the idle loop
> > > > either.
> > >
> > > BTW, the perf numbers were not from an RT kernel, they were from my
> > > PREEMPT_VOLUNTARY desktop kernel.
> >
> > Can we move quiet_vmstat() elsewhere after we have checked that really
> > nothing else is going on soon?
>
> How would you check?  Precognition doesn't work for mortals.

Dont we have some decision mechanism to go into higher levels of power
savings when the system is idle for longer times?