From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Matthew Whitehead <tedheadster@gmail.com>,
john.stultz@linaro.org, linux-kernel@vger.kernel.org,
mwhitehe@redhat.com
Subject: Re: nohz problem with idle time on old hardware
Date: Wed, 13 Nov 2013 08:18:29 -0800 [thread overview]
Message-ID: <20131113161829.GE4138@linux.vnet.ibm.com> (raw)
In-Reply-To: <20131113111257.482c2955@gandalf.local.home>
On Wed, Nov 13, 2013 at 11:12:57AM -0500, Steven Rostedt wrote:
> On Wed, 13 Nov 2013 17:07:18 +0100 (CET)
> Thomas Gleixner <tglx@linutronix.de> wrote:
>
>
> > Right. It's telling you if NOHZ is enabled. It's not telling you that
> > NOHZ is active.
>
> Yeah, which makes this code rather silly:
>
> in rcu_prepare_for_idle():
>
> /* Handle nohz enablement switches conservatively. */
> tne = ACCESS_ONCE(tick_nohz_enabled);
> if (tne != rdtp->tick_nohz_enabled_snap) {
> if (rcu_cpu_has_callbacks(cpu, NULL))
> invoke_rcu_core(); /* force nohz to see update. */
> rdtp->tick_nohz_enabled_snap = tne;
> return;
> }
OK, what should I be checking instead? Not much point in trying to
get RCU out of the way of disabling the scheduling-clock interrupt
if NOHZ is disabled. ;-)
Thanx, Paul
next prev parent reply other threads:[~2013-11-13 16:18 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-13 11:39 nohz problem with idle time on old hardware Matthew Whitehead
2013-11-13 14:02 ` Thomas Gleixner
2013-11-13 15:21 ` Steven Rostedt
2013-11-13 15:31 ` Steven Rostedt
2013-11-13 15:50 ` Thomas Gleixner
2013-11-13 16:17 ` Paul E. McKenney
2013-11-13 15:57 ` Steven Rostedt
2013-11-13 16:07 ` Thomas Gleixner
2013-11-13 16:12 ` Steven Rostedt
2013-11-13 16:18 ` Paul E. McKenney [this message]
2013-11-13 16:23 ` Steven Rostedt
2013-11-13 16:35 ` Paul E. McKenney
2013-11-13 20:01 ` Thomas Gleixner
2013-11-13 20:07 ` Steven Rostedt
2013-11-13 21:49 ` Matthew Whitehead
2013-11-18 22:44 ` Paul E. McKenney
2013-11-19 18:07 ` [tip:timers/urgent] NOHZ: Check for nohz active instead of nohz enabled tip-bot for Thomas Gleixner
2014-04-09 13:51 ` nohz problem with idle time on old hardware Viresh Kumar
2014-04-09 14:31 ` Steven Rostedt
2014-04-09 15:20 ` Viresh Kumar
2014-04-09 15:29 ` Steven Rostedt
2014-04-09 15:31 ` Steven Rostedt
2014-04-09 15:34 ` Viresh Kumar
2014-04-09 15:39 ` Steven Rostedt
2014-04-09 15:56 ` Viresh Kumar
2014-04-09 16:15 ` Steven Rostedt
2014-04-09 15:11 ` Frederic Weisbecker
2013-11-13 16:21 ` Thomas Gleixner
2013-11-13 16:31 ` Steven Rostedt
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