linux-kernel - Re: [PATCH V5 2/2] tracing, perf : add cpu hotplug trace events

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Date:	Thu, 24 Feb 2011 19:46:37 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Vincent Guittot <vincent.guittot@...aro.org>
Cc:	linux-kernel@...r.kernel.org, linux-hotplug@...r.kernel.org,
	Frederic Weisbecker <fweisbec@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>, amit.kucheria@...aro.org,
	Rusty Russell <rusty@...tcorp.com.au>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH V5 2/2] tracing, perf : add cpu hotplug trace events

On Thu, 2011-02-24 at 18:33 +0100, Vincent Guittot wrote:

> 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.

> this patch adds new events for cpu hotplug tracing
>  * plug/unplug sequence
>  * core and architecture latency measurements

Aside of the points tglx made, I do have to ask _WHY_!?

Anybody who is interested in the latency of cpu hotplug is deluding
himself, also cpu hotplug is _NOT_ a power management feature, so the
rest of your justification just disappeared as well.


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