linux-kernel - Re: [RFC GIT PULL] nohz: Full dynticks rq clock handling

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Message-ID: <20130410102948.GB28505@gmail.com>
Date:	Wed, 10 Apr 2013 12:29:48 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Alessio Igor Bogani <abogani@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Chris Metcalf <cmetcalf@...era.com>,
	Christoph Lameter <cl@...ux.com>,
	Geoff Levand <geoff@...radead.org>,
	Gilad Ben Yossef <gilad@...yossef.com>,
	Hakan Akkan <hakanakkan@...il.com>,
	Li Zhong <zhong@...ux.vnet.ibm.com>,
	Namhyung Kim <namhyung.kim@....com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Paul Turner <pjt@...gle.com>, Mike Galbraith <efault@....de>
Subject: Re: [RFC GIT PULL] nohz: Full dynticks rq clock handling


* Peter Zijlstra <peterz@...radead.org> wrote:

> Another thing I just noticed; our update_curr() assumes its called at least once 
> every 4 odd seconds (2^32 ns like).
> 
> update_curr() is 'required' for things like task runtime stats and everything 
> that hangs off of that like cputimers etc.
> 
> Now I'm not entirely sure how the nr_running==1 nohz case deals with this, but I 
> can imagine it might take a while. In this case we might need to 'fix' 
> update_curr() to not asume the time delta fits in 32 bits.

Good point ...

Thanks,

	Ingo
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