linux-kernel - Re: [PATCH v2 0/6] ftrace: to kill a daemon (small updates)

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Message-ID: <20080815092412.GC22209@elte.hu>
Date:	Fri, 15 Aug 2008 11:24:12 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	David Miller <davem@...emloft.net>,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	Roland McGrath <roland@...hat.com>,
	Ulrich Drepper <drepper@...hat.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Gregory Haskins <ghaskins@...ell.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	"Luis Claudio R. Goncalves" <lclaudio@...g.org>,
	Clark Williams <williams@...hat.com>,
	Bruce Duncan <bwduncan@...il.com>,
	Marcin Slusarz <marcin.slusarz@...il.com>,
	Steven Rostedt <srostedt@...hat.com>
Subject: Re: [PATCH v2 0/6] ftrace: to kill a daemon (small updates)


* Steven Rostedt <rostedt@...dmis.org> wrote:

> [
>   Changes since v1:
> 
>     regex fix in x86_64 recordmcount.pl. Now it can handle all
>       mcount+0x... mcount-0x... and mcount, where as the original
>       only handled mcount+0x...
> 
>     Made mcount on start-up to simply return. The current mcount
>       is set up to be replaced with a call to ftrace_record_ip.
>       This is no longer necessary.
> 
>   Note: This patch series is focusing on how calls to mcount in
>     the kernel are converted to nops. It does not address what
>     kind of nop is used. That is a different topic, and should
>     be in a different patch series.
> 
>   Note 2: I have found that the changes here are more stable than
>     the current daemon method, and these patches should be used.
>     It also solves the resume from suspend to ram bug that was
>     reported:
> 
>       http://lkml.org/lkml/2008/8/12/234
>        and
>       http://lkml.org/lkml/2008/8/12/451
> 
>   Note 3: I have already ported this to PowerPC64, but I am waiting
>     for this to be accepted first before submitting those changes.
> ]
> 
> One of the things that bothered me about the latest ftrace code was 
> this annoying daemon that would wake up once a second to see if it had 
> work to do. If it did not, it would go to sleep, otherwise it would do 
> its work and then go to sleep.

i like this concept alot - i've applied the whole lot to 
tip/tracing/ftrace.

Eventually gcc should be extended to provide a separate section for 
instrumentation patch sites, instead of us having to disassemble the 
object code. That would also make the ftrace build faster. Any gcc folks 
interested in that?

	Ingo
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