linux-kernel - Re: RFC vmstat: On demand vmstat threads

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Date:	Fri, 20 Sep 2013 12:41:02 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Christoph Lameter <cl@...ux.com>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Gilad Ben-Yossef <gilad@...yossef.com>,
	Tejun Heo <tj@...nel.org>, John Stultz <johnstul@...ibm.com>,
	Mike Frysinger <vapier@...too.org>,
	Minchan Kim <minchan.kim@...il.com>,
	Hakan Akkan <hakanakkan@...il.com>,
	Max Krasnyansky <maxk@...lcomm.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Linux-MM <linux-mm@...ck.org>
Subject: Re: RFC vmstat: On demand vmstat threads

On Thu, 19 Sep 2013, Christoph Lameter wrote:
> On Thu, 19 Sep 2013, Thomas Gleixner wrote:
> 
> > The vmstat accounting is not the only thing which we want to delegate
> > to dedicated core(s) for the full NOHZ mode.
> >
> > So instead of playing broken games with explicitly not exposed core
> > code variables, we should implement a core code facility which is
> > aware of the NOHZ details and provides a sane way to delegate stuff to
> > a certain subset of CPUs.
> 
> I would be happy to use such a facility. Otherwise I would just be adding
> yet another kernel option or boot parameter I guess.

Uuurgh, no.

The whole delegation stuff is necessary not just for vmstat. We have
the same issue for scheduler stats and other parts of the kernel, so
we are better off in having a core facility to schedule such functions
in consistency with the current full NOHZ state.

Thanks,

	tglx



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