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From: Peter Zijlstra <peterz@infradead.org>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Alessio Igor Bogani <abogani@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Chris Metcalf <cmetcalf@tilera.com>,
	Christoph Lameter <cl@linux.com>,
	Geoff Levand <geoff@infradead.org>,
	Gilad Ben Yossef <gilad@benyossef.com>,
	Hakan Akkan <hakanakkan@gmail.com>,
	Li Zhong <zhong@linux.vnet.ibm.com>,
	Namhyung Kim <namhyung.kim@lge.com>,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
	Paul Gortmaker <paul.gortmaker@windriver.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Paul Turner <pjt@google.com>, Mike Galbraith <efault@gmx.de>
Subject: Re: [PATCH 1/7] sched: Update rq clock on nohz CPU before migrating tasks
Date: Tue, 09 Apr 2013 11:13:04 +0200	[thread overview]
Message-ID: <1365498784.2609.165.camel@laptop> (raw)
In-Reply-To: <1365266760-24725-2-git-send-email-fweisbec@gmail.com>

On Sat, 2013-04-06 at 18:45 +0200, Frederic Weisbecker wrote:
> Because the sched_class::put_prev_task() callback of rt and fair
> classes are referring to the rq clock to update their runtime
> statistics. A CPU running in tickless mode may carry a stale value.
> We need to update it there.

I'm failing to see how tickless makes a difference here.. we should
never rely on a ->clock set at the last tick, that's wrong.

So either explain which/how clock update gets lost by tickless or make
it unconditional.


  parent reply	other threads:[~2013-04-09  9:13 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-04-06 16:45 [RFC GIT PULL] nohz: Full dynticks rq clock handling Frederic Weisbecker
2013-04-06 16:45 ` [PATCH 1/7] sched: Update rq clock on nohz CPU before migrating tasks Frederic Weisbecker
2013-04-08 11:48   ` Ingo Molnar
2013-04-09  9:13   ` Peter Zijlstra [this message]
2013-04-09 13:11     ` Frederic Weisbecker
2013-04-06 16:45 ` [PATCH 2/7] sched: Update rq clock on nohz CPU before setting fair group shares Frederic Weisbecker
2013-04-09  9:26   ` Peter Zijlstra
2013-04-09 13:21     ` Frederic Weisbecker
2013-04-10  7:05       ` Peter Zijlstra
2013-04-10 10:06         ` Ingo Molnar
2013-04-10 11:02           ` Peter Zijlstra
2013-04-10 11:06             ` Ingo Molnar
2013-04-10 11:47               ` Peter Zijlstra
2013-04-10 11:50                 ` Ingo Molnar
2013-04-06 16:45 ` [PATCH 3/7] sched: Update rq clock on tickless CPUs before calling check_preempt_curr() Frederic Weisbecker
2013-04-09 13:18   ` Peter Zijlstra
2013-04-09 16:53     ` Frederic Weisbecker
2013-04-06 16:45 ` [PATCH 4/7] sched: Update rq clock earlier in unthrottle_cfs_rq Frederic Weisbecker
2013-04-06 16:45 ` [PATCH 5/7] sched: Update rq clock before idle balancing Frederic Weisbecker
2013-04-06 16:45 ` [PATCH 6/7] sched: Use an accessor to read rq clock Frederic Weisbecker
2013-04-06 16:46 ` [PATCH 7/7] sched: Debug nohz " Frederic Weisbecker
2013-04-10 10:26 ` [RFC GIT PULL] nohz: Full dynticks rq clock handling Peter Zijlstra
2013-04-10 10:29   ` Ingo Molnar
2013-04-11 15:11   ` Frederic Weisbecker

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