From: Frederic Weisbecker <fweisbec@gmail.com>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: LKML <linux-kernel@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Ingo Molnar <mingo@elte.hu>, Steven Rostedt <rostedt@goodmis.org>,
Lai Jiangshan <laijs@cn.fujitsu.com>,
Andrew Morton <akpm@linux-foundation.org>,
Anton Blanchard <anton@au1.ibm.com>,
Tim Pepper <lnxninja@linux.vnet.ibm.com>
Subject: Re: [RFC PATCH 10/15] nohz_task: Enter in extended quiescent state when in userspace
Date: Tue, 21 Dec 2010 02:27:44 +0100 [thread overview]
Message-ID: <20101221012742.GJ1715@nowhere> (raw)
In-Reply-To: <1292861920.5021.29.camel@laptop>
On Mon, Dec 20, 2010 at 05:18:40PM +0100, Peter Zijlstra wrote:
> On Mon, 2010-12-20 at 16:24 +0100, Frederic Weisbecker wrote:
> > (we check if the local cpu is in nohz mode, which means
> > no other task compete on that CPU)
>
> You keep repeating that definition, but its not true.. It means there is
> not work for the tick to do, the tick does _tons_ more besides
> preemption, so nr_running==1 is necessary but not sufficient.
Sure but the point is that if the tick is not running, it means
that the nohz task is the only task running on that CPU.
Now indeed there are other reasons for the tick to restart like RCU
or the effective nohz mode to physically happen or to be delayed,
which is decided by tick_nohz_stop_sched_tick().
next prev parent reply other threads:[~2010-12-21 1:27 UTC|newest]
Thread overview: 98+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-12-20 15:24 [RFC PATCH 00/15] Nohz task support Frederic Weisbecker
2010-12-20 15:24 ` [RFC PATCH 01/15] nohz_task: New mask for cpus having nohz task Frederic Weisbecker
2010-12-24 8:00 ` Lai Jiangshan
2010-12-24 8:19 ` Dario Faggioli
2010-12-24 12:29 ` Frederic Weisbecker
2010-12-20 15:24 ` [RFC PATCH 02/15] nohz_task: Avoid nohz task cpu as non-idle timer target Frederic Weisbecker
2010-12-20 15:47 ` Peter Zijlstra
2010-12-20 16:06 ` Steven Rostedt
2010-12-20 16:12 ` Peter Zijlstra
2010-12-21 0:20 ` Frederic Weisbecker
2010-12-21 7:51 ` Peter Zijlstra
2010-12-21 13:58 ` Frederic Weisbecker
2010-12-21 0:13 ` Frederic Weisbecker
2010-12-21 7:50 ` Peter Zijlstra
2010-12-21 13:52 ` Frederic Weisbecker
2010-12-20 15:24 ` [RFC PATCH 03/15] nohz_task: Make tick stop and restart callable outside idle Frederic Weisbecker
2010-12-20 15:48 ` Peter Zijlstra
2010-12-20 16:19 ` Steven Rostedt
2010-12-20 16:25 ` Peter Zijlstra
2010-12-21 1:34 ` Frederic Weisbecker
2010-12-20 15:24 ` [RFC PATCH 04/15] nohz_task: Stop the tick when the nohz task runs alone Frederic Weisbecker
2010-12-20 15:51 ` Peter Zijlstra
2010-12-20 23:37 ` Frederic Weisbecker
2010-12-21 7:35 ` Peter Zijlstra
2010-12-21 13:22 ` Frederic Weisbecker
2010-12-21 14:34 ` Steven Rostedt
2010-12-21 15:14 ` Frederic Weisbecker
2010-12-20 15:24 ` [RFC PATCH 05/15] nohz_task: Restart the tick when another task compete on the cpu Frederic Weisbecker
2010-12-20 15:53 ` Peter Zijlstra
2010-12-20 23:39 ` Frederic Weisbecker
2010-12-20 15:24 ` [RFC PATCH 06/15] nohz_task: Keep the tick if rcu needs it Frederic Weisbecker
2010-12-20 15:58 ` Peter Zijlstra
2010-12-20 23:49 ` Frederic Weisbecker
2010-12-21 0:12 ` Jonathan Corbet
2010-12-21 2:10 ` Frederic Weisbecker
2010-12-21 8:10 ` Paul E. McKenney
2010-12-20 15:24 ` [RFC PATCH 07/15] nohz_task: Restart tick when RCU forces nohz task cpu quiescent state Frederic Weisbecker
2010-12-20 16:02 ` Peter Zijlstra
2010-12-20 23:52 ` Frederic Weisbecker
2010-12-21 7:41 ` Peter Zijlstra
2010-12-21 13:28 ` Frederic Weisbecker
2010-12-21 15:35 ` Paul E. McKenney
2010-12-20 15:24 ` [RFC PATCH 08/15] smp: Don't warn if irq are disabled but we don't wait for the ipi Frederic Weisbecker
2010-12-20 16:03 ` Peter Zijlstra
2010-12-21 0:02 ` Frederic Weisbecker
2010-12-20 15:24 ` [RFC PATCH 09/15] rcu: Make rcu_enter,exit_nohz() callable from irq Frederic Weisbecker
2010-12-21 19:26 ` Paul E. McKenney
2010-12-21 19:27 ` Frederic Weisbecker
2010-12-20 15:24 ` [RFC PATCH 10/15] nohz_task: Enter in extended quiescent state when in userspace Frederic Weisbecker
2010-12-20 16:18 ` Peter Zijlstra
2010-12-21 1:27 ` Frederic Weisbecker [this message]
2010-12-21 8:04 ` Peter Zijlstra
2010-12-21 14:06 ` Frederic Weisbecker
2010-12-21 19:28 ` Paul E. McKenney
2010-12-21 21:49 ` Frederic Weisbecker
2010-12-22 2:20 ` Paul E. McKenney
2010-12-20 15:24 ` [RFC PATCH 11/15] x86: Nohz task support Frederic Weisbecker
2010-12-20 16:23 ` Peter Zijlstra
2010-12-21 1:30 ` Frederic Weisbecker
2010-12-21 8:05 ` Peter Zijlstra
2010-12-21 14:19 ` Frederic Weisbecker
2010-12-21 15:12 ` Frederic Weisbecker
2010-12-20 15:24 ` [RFC PATCH 12/15] clocksource: Ignore nohz task cpu in clocksource watchdog Frederic Weisbecker
2010-12-20 16:27 ` Peter Zijlstra
2010-12-21 1:40 ` Frederic Weisbecker
2010-12-20 15:24 ` [RFC PATCH 13/15] sched: Protect nohz task cpu affinity Frederic Weisbecker
2010-12-20 16:28 ` Peter Zijlstra
2010-12-20 17:05 ` Steven Rostedt
2010-12-21 1:55 ` Frederic Weisbecker
2010-12-20 15:24 ` [RFC PATCH 14/15] nohz_task: Clear nohz task attribute on exit() Frederic Weisbecker
2010-12-20 16:30 ` Peter Zijlstra
2010-12-21 1:48 ` Frederic Weisbecker
2010-12-21 8:07 ` Peter Zijlstra
2010-12-21 14:22 ` Frederic Weisbecker
2010-12-20 15:24 ` [RFC PATCH 15/15] nohz_task: Procfs interface Frederic Weisbecker
2010-12-20 15:42 ` Peter Zijlstra
2010-12-20 15:57 ` Frederic Weisbecker
2010-12-20 16:16 ` Peter Zijlstra
2010-12-21 1:24 ` Frederic Weisbecker
2010-12-21 8:14 ` Peter Zijlstra
2010-12-21 14:00 ` Avi Kivity
2010-12-21 17:05 ` Frederic Weisbecker
2010-12-21 18:17 ` Avi Kivity
2010-12-21 21:08 ` Frederic Weisbecker
2010-12-22 9:22 ` Avi Kivity
2010-12-22 9:51 ` Peter Zijlstra
2010-12-22 20:41 ` Frederic Weisbecker
2010-12-21 14:26 ` Frederic Weisbecker
2010-12-20 15:44 ` [RFC PATCH 00/15] Nohz task support Steven Rostedt
2010-12-20 23:33 ` Frederic Weisbecker
2010-12-21 1:36 ` Steven Rostedt
2010-12-21 2:15 ` Frederic Weisbecker
2010-12-21 7:34 ` Peter Zijlstra
2010-12-21 13:13 ` Frederic Weisbecker
2010-12-21 13:56 ` Avi Kivity
2010-12-21 17:01 ` Frederic Weisbecker
2010-12-20 16:35 ` Peter Zijlstra
2010-12-21 1:53 ` Frederic Weisbecker
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