linux-kernel - Re: Fix powerTOP regression with 2.6.39-rc5

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Message-ID: <4DC58888.9030402@linux.intel.com>
Date:	Sat, 07 May 2011 10:59:36 -0700
From:	Arjan van de Ven <arjan@...ux.intel.com>
To:	Steven Rostedt <rostedt@...dmis.org>
CC:	Ingo Molnar <mingo@...e.hu>, David Sharp <dhsharp@...gle.com>,
	Vaibhav Nagarnaik <vnagarnaik@...gle.com>,
	Michael Rubin <mrubin@...gle.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: Fix powerTOP regression with 2.6.39-rc5

On 5/7/2011 10:20 AM, Steven Rostedt wrote:
> On Sat, 2011-05-07 at 16:44 +0200, Ingo Molnar wrote:
>> * Steven Rostedt<rostedt@...dmis.org>  wrote:
>>
>>> 2) we separate perf from ftrace and keep the "stable" ABI for perf, and let
>>> ftrace advance into a more efficient tracer.
>> The thing is, ftrace is still largely separated from perf, and this is why this
>> regression came in: a random tracing 'cleanup' churn was done to 'tracing'
>> which broke PowerTop.
>>
>> Look at the commit itself:
>>
>>    e6e1e2593592: tracing: Remove lock_depth from event entry
>>
>> Clearly you didnt even *realize* that there's a whole tooling world behind this
>> mechanism ...
> Note, I discussed this change with Frederic and he totally agreed with
> me on removing it. In fact, we are in discussions about getting rid of
> pid, preempt-count, and irq flags as well. But according to your logic,
> that is a no go. I guess Frederic also does not *realize* there's a
> whole tooling world behind this mechanism too.

btw if you remove some of these, how is userland supposed to find out if 
an event happened in irq context?


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