linux-kernel - Re: [PATCH 2/2] tracing, perf : add cpu hotplug trace events

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Message-ID: <20110128175410.GB1761@nowhere>
Date:	Fri, 28 Jan 2011 18:54:14 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Vincent Guittot <vincent.guittot@...aro.org>
Cc:	linux-kernel@...r.kernel.org, linux-hotplug@...r.kernel.org,
	rostedt@...dmis.org, amit.kucheria@...aro.org
Subject: Re: [PATCH 2/2] tracing, perf : add cpu hotplug trace events

On Thu, Jan 27, 2011 at 11:04:09AM +0100, Vincent Guittot wrote:
> On 26 January 2011 18:32, Frederic Weisbecker <fweisbec@...il.com> wrote:
> > On Tue, Jan 25, 2011 at 09:54:59AM +0100, Vincent Guittot wrote:
> >> Please find below a new proposal for adding trace events for cpu hotplug.
> >> 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.
> >>
> >> Subject: [PATCH 1/2] add cpu hotplug tracepoints
> >>
> >> this patch adds new events for cpu hotplug tracing
> >>  * plug/unplug sequence
> >>  * core and architecture latency measurements
> >>
> >> Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>
> >> ---
> >>  kernel/cpu.c |   17 +++++++++++++++++
> >>  1 files changed, 17 insertions(+), 0 deletions(-)
> >>
> >> diff --git a/kernel/cpu.c b/kernel/cpu.c
> >> index 156cc55..f04e9cf 100644
> >> --- a/kernel/cpu.c
> >> +++ b/kernel/cpu.c
> >> @@ -16,6 +16,9 @@
> >>  #include <linux/mutex.h>
> >>  #include <linux/gfp.h>
> >>
> >> +#define CREATE_TRACE_POINTS
> >> +#include <trace/events/cpu_hotplug.h>
> >> +
> >>  #ifdef CONFIG_SMP
> >>  /* Serializes the updates to cpu_online_mask, cpu_present_mask */
> >>  static DEFINE_MUTEX(cpu_add_remove_lock);
> >> @@ -200,7 +203,9 @@ static int __ref take_cpu_down(void *_param)
> >>       int err;
> >>
> >>       /* Ensure this CPU doesn't handle any more interrupts. */
> >> +     trace_cpu_hotplug_arch_disable_start((unsigned int)(param->hcpu));
> >>       err = __cpu_disable();
> >> +     trace_cpu_hotplug_arch_disable_end((unsigned int)(param->hcpu));
> >
> > You should create a cpu var instead of doing that not very beautiful cast
> > twice.
> >
> 
> OK
> 
> > Probably we should eventually rename arch_disable into just disable.
> >
> > And same for die, because otherwise the name is quite long.
> >
> 
> If we remove the arch extension of these names, we will have
> trace_cpu_hotplug_arch_up for __cpu_up (trace_cpu_hotplug_up is
> already used) and trace_cpu_hotplug_disable for __cpu_disable. would
> that be acceptable ?

You're right.

Well, we could rename cpu_hotplug_arch_up into cpu_hotplug_enable,
but the overall result makes it confusing.

Let's keep it that way.
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