From: Mike Galbraith <umgwanakikbuti@gmail.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: LKML <linux-kernel@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@elte.hu>, Steven Rostedt <rostedt@goodmis.org>
Subject: Re: RFC: futex_wait() can DoS the tick
Date: Thu, 11 Jun 2015 13:41:15 +0200 [thread overview]
Message-ID: <1434022875.4051.5.camel@gmail.com> (raw)
In-Reply-To: <alpine.DEB.2.11.1506111030350.3786@nanos>
On Thu, 2015-06-11 at 10:34 +0200, Thomas Gleixner wrote:
> Can you try the following, please?
>
> Enable function tracer and hrtimer events manually. Then watch the irq
> count on cpu3. If it stalls or becomes slow, then stop the trace with
>
> echo 0 >/sys/kernel/debug/tracing/tracing_on
>
> If the overhead of the function tracer hides the problem, then try just
> with hrtimer, sched_switch and irq events.
Yeah, function tracer hides it. After some fiddling with buffer size to
be able to ever see a tick, I finally have a trace trimmed with a tick
on each end, 175ms gap between them. It's still 1.5 after xz, sending
off list.
-Mike
next prev parent reply other threads:[~2015-06-11 11:41 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-10 12:44 RFC: futex_wait() can DoS the tick Mike Galbraith
2015-06-10 15:12 ` Thomas Gleixner
2015-06-10 16:29 ` Mike Galbraith
2015-06-10 18:27 ` Thomas Gleixner
2015-06-10 17:30 ` Mike Galbraith
2015-06-10 18:59 ` Thomas Gleixner
2015-06-10 19:15 ` Steven Rostedt
2015-06-10 19:32 ` Thomas Gleixner
2015-06-11 2:27 ` Mike Galbraith
2015-06-11 8:34 ` Thomas Gleixner
2015-06-11 11:41 ` Mike Galbraith [this message]
2015-06-11 13:13 ` Thomas Gleixner
2015-06-11 13:58 ` Mike Galbraith
2015-06-11 18:43 ` Mike Galbraith
2015-06-11 18:52 ` Thomas Gleixner
2015-06-11 18:55 ` Mike Galbraith
2015-06-11 7:35 ` Mike Galbraith
2015-06-11 7:43 ` Mike Galbraith
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