From: Don Zickus <dzickus@redhat.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
Frederic Weisbecker <fweisbec@gmail.com>,
Ingo Molnar <mingo@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Andrew Morton <akpm@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
"H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [PATCH 1/2] nohz: Disable LOCKUP_DETECTOR when NO_HZ_FULL is enabled
Date: Wed, 15 May 2013 12:26:54 -0400 [thread overview]
Message-ID: <20130515162654.GR23604@redhat.com> (raw)
In-Reply-To: <1368631622.6828.69.camel@gandalf.local.home>
On Wed, May 15, 2013 at 11:27:02AM -0400, Steven Rostedt wrote:
> > Coming into the middle of the thread is always hard, but why/how does perf
> > disable nohz_full? I didn't think the hardware events of perf would cause
> > problems as they are no different than an irq. Curious.
>
> Right now perf requires a tick, not sure exactly why, but you can look
> at the code in perf_event_task_tick(). Thus if NO_HZ_FULL sees that a
> perf tick is pending, it won't disable ticks. Unfortunately, the
> watchdogs, both NMI and soft lockup, use the perf infrastructure to
> trigger NMIs or interrupts. This adds a perf element on the rotate list
> and keeps NO_HZ_FULL from *ever* activating.
Ok. Thanks. I don't know what the rotate list is for (nor what it does
in general). But I'll poke around.
Cheers,
Don
next prev parent reply other threads:[~2013-05-15 16:08 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-14 16:02 [GIT PULL] Nohz fixes Frederic Weisbecker
2013-05-14 16:02 ` [PATCH 1/2] nohz: Disable LOCKUP_DETECTOR when NO_HZ_FULL is enabled Frederic Weisbecker
2013-05-15 8:37 ` Peter Zijlstra
2013-05-15 15:06 ` Don Zickus
2013-05-15 15:27 ` Steven Rostedt
2013-05-15 16:26 ` Don Zickus [this message]
2013-05-15 16:59 ` Peter Zijlstra
2013-05-15 17:04 ` Steven Rostedt
2013-05-16 8:10 ` Peter Zijlstra
2013-05-16 11:38 ` Frederic Weisbecker
2013-05-16 17:57 ` Peter Zijlstra
2013-05-16 15:07 ` Paul E. McKenney
2013-05-16 17:56 ` Peter Zijlstra
2013-05-16 18:32 ` Steven Rostedt
2013-05-16 23:14 ` Frederic Weisbecker
2013-05-19 16:18 ` Paul E. McKenney
2013-05-16 20:06 ` Paul E. McKenney
2013-05-15 17:11 ` Peter Zijlstra
2013-05-15 17:50 ` Don Zickus
2013-05-15 16:55 ` Peter Zijlstra
2013-05-15 15:59 ` Frederic Weisbecker
2013-05-14 16:02 ` [PATCH 2/2] nohz: Warn if the machine can not perform nohz_full Frederic Weisbecker
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