From: Ingo Molnar <mingo@elte.hu>
To: "Frédéric Weisbecker" <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>,
Linux Kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] tracing/ftrace: use preempt_enable_no_resched_notrace in ring_buffer_time_stamp()
Date: Tue, 16 Dec 2008 22:59:41 +0100 [thread overview]
Message-ID: <20081216215941.GA14787@elte.hu> (raw)
In-Reply-To: <c62985530812161355l11edbb9cg6dd4e7e4291ab7b@mail.gmail.com>
* Frédéric Weisbecker <fweisbec@gmail.com> wrote:
> 2008/12/16 Steven Rostedt <rostedt@goodmis.org>:
> >
> >
> > On Tue, 16 Dec 2008, Fr?d?ric Weisbecker wrote:
> >>
> >> The hard reboots I've seen are related to x86-64 while
> >> disabling/reenabling a CPU through /sys/device/system/cpu
> >> No tracer was enabled at these times (the problem still remains with
> >> latest updates on -tip for half an hour).
> >
> > Do you have STACK_TRACER enabled?
> >
> > -- Steve
> >
>
> You were right. I've just built a kernel without STACK_TRACER and the
> problem disappears...
i noticed high stack-tracer overhead too. Which is understandable i guess:
the stack tracer keeps the mcount callbacks running all the time and can
save the stack backtrace of the highest-stack-usage point in time that the
kernel ever has hit in the past. That is a pretty powerful debug
capability, with appropriate costs.
Ingo
next prev parent reply other threads:[~2008-12-16 22:00 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-12-16 21:08 [PATCH] tracing/ftrace: use preempt_enable_no_resched_notrace in ring_buffer_time_stamp() Frederic Weisbecker
2008-12-16 21:20 ` Ingo Molnar
2008-12-16 21:39 ` Frédéric Weisbecker
2008-12-16 21:43 ` Steven Rostedt
2008-12-16 21:48 ` Frédéric Weisbecker
2008-12-16 21:55 ` Frédéric Weisbecker
2008-12-16 21:59 ` Ingo Molnar [this message]
2008-12-16 22:53 ` Steven Rostedt
2008-12-16 21:50 ` Ingo Molnar
2008-12-16 22:38 ` Frédéric Weisbecker
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