linux-kernel - Re: [PATCH V2] tracing, perf : add cpu hotplug trace events

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Date:	Fri, 21 Jan 2011 09:43:18 +0100
From:	Vincent Guittot <vincent.guittot@...aro.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	linux-kernel@...r.kernel.org, linux-hotplug@...r.kernel.org,
	rostedt@...dmis.org, amit.kucheria@...aro.org
Subject: Re: [PATCH V2] tracing, perf : add cpu hotplug trace events

On 20 January 2011 17:11, Frederic Weisbecker <fweisbec@...il.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 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.
>>
>> 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
>>  * plug/unplug sequence
>>  * core and architecture latency measurements
>>
>> Signed-off-by: Vincent Guittot <vincent.guittot@...aro.com>
>> ---
>>  include/trace/events/cpu_hotplug.h |  117 ++++++++++++++++++++++++++++++++++++
>
> Note we can't apply new tracepoints if they are not inserted in the code.

I agree, i just want to have 1st feedbacks on the tracepoint interface
before providing a patch which inserts the trace in the code.

>
>> +DEFINE_EVENT(cpu_hotplug, cpu_hotplug_arch_wait_die_start,
>> +
>> +     TP_PROTO(unsigned int cpuid),
>> +
>> +     TP_ARGS(cpuid)
>> +);
>> +
>> +DEFINE_EVENT(cpu_hotplug, cpu_hotplug_arch_wait_die_end,
>> +
>> +     TP_PROTO(unsigned int cpuid),
>> +
>> +     TP_ARGS(cpuid)
>> +);
>
> What is wait die, compared to die for example?
>

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)

> We need those tracepoints to be applied to get that reviewable in practice.
>

Ok, I'm going to send a proposal

> Thanks.
>
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