From mboxrd@z Thu Jan  1 00:00:00 1970
From: Frederic Weisbecker <fweisbec@gmail.com>
Date: Fri, 21 Jan 2011 16:44:07 +0000
Subject: Re: [PATCH V2] tracing, perf : add cpu hotplug trace events
Message-Id: <20110121164404.GA2520@nowhere>
List-Id: <linux-hotplug.vger.kernel.org>
References: <AANLkTinNoYbDe5huY4_Q6YidbWxqXqVWbVP2_7o-=P3W@mail.gmail.com>
 <20110120161101.GA17218@nowhere>
 <AANLkTinhX6UwQA0HFhuu5=jbq84woVhqtahuzA5hEo2o@mail.gmail.com>
In-Reply-To: <AANLkTinhX6UwQA0HFhuu5=jbq84woVhqtahuzA5hEo2o@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
To: Vincent Guittot <vincent.guittot@linaro.org>
Cc: linux-kernel@vger.kernel.org, linux-hotplug@vger.kernel.org, rostedt@goodmis.org, amit.kucheria@linaro.org

On Fri, Jan 21, 2011 at 09:43:18AM +0100, Vincent Guittot wrote:
> On 20 January 2011 17:11, Frederic Weisbecker <fweisbec@gmail.com> wrote:
> > On Thu, Jan 20, 2011 at 09:25:54AM +0100, Vincent Guittot wrote:
> >> Please find below a new proposal for adding trace events for cpu hotpl=
ug.
> >> The goal is to measure the latency of each part (kernel, architecture)
> >> and also to trace the cpu hotplug activity with other power events. I
> >> have tested these traces events on an arm platform.
> >>
> >> Changes since previous version:
> >> -Use cpu_hotplug for trace name
> >> -Define traces for kernel core and arch parts only
> >> -Use DECLARE_EVENT_CLASS and DEFINE_EVENT
> >> -Use proper indentation
> >>
> >> Subject: [PATCH] cpu hotplug tracepoint
> >>
> >> this patch adds new events for cpu hotplug tracing
> >> =A0* plug/unplug sequence
> >> =A0* core and architecture latency measurements
> >>
> >> Signed-off-by: Vincent Guittot <vincent.guittot@linaro.com>
> >> ---
> >> =A0include/trace/events/cpu_hotplug.h | =A0117 +++++++++++++++++++++++=
+++++++++++++
> >
> > Note we can't apply new tracepoints if they are not inserted in the cod=
e.
>=20
> I agree, i just want to have 1st feedbacks on the tracepoint interface
> before providing a patch which inserts the trace in the code.
>=20
> >
> >> +DEFINE_EVENT(cpu_hotplug, cpu_hotplug_arch_wait_die_start,
> >> +
> >> + =A0 =A0 TP_PROTO(unsigned int cpuid),
> >> +
> >> + =A0 =A0 TP_ARGS(cpuid)
> >> +);
> >> +
> >> +DEFINE_EVENT(cpu_hotplug, cpu_hotplug_arch_wait_die_end,
> >> +
> >> + =A0 =A0 TP_PROTO(unsigned int cpuid),
> >> +
> >> + =A0 =A0 TP_ARGS(cpuid)
> >> +);
> >
> > What is wait die, compared to die for example?
> >
>=20
> The arch_wait_die is used to trace the process which waits for the cpu
> to die (__cpu_die) and the arch_die is used to trace when the cpu dies
> (cpu_die)

I still can't find the difference.

Having:

trace_cpu_hotplug_arch_die_start(cpu)
__cpu_die();
trace_cpu_hotplug_arch_die_end(cpu)

Is not enough to get both the information that a cpu dies
and the time took to do so?