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

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Date:	Wed, 10 Apr 2013 12:26:43 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Ingo Molnar <mingo@...nel.org>,
	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


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.

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