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From: Jan Kiszka <jan.kiszka@siemens.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
	Frederic Weisbecker <fweisbec@gmail.com>,
	Abhishek Sagar <sagar.abhishek@gmail.com>,
	"David S. Miller" <davem@davemloft.net>,
	Thomas Gleixner <tglx@linutronix.de>,
	Peter Zijlstra <peterz@infradead.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Steven Rostedt <srostedt@redhat.com>
Subject: Re: [PATCH 08/13 v2] ftrace: do not trace init sections
Date: Thu, 23 Oct 2008 13:15:28 +0200	[thread overview]
Message-ID: <49005CD0.2070807@siemens.com> (raw)
In-Reply-To: <20081022213552.440512191@goodmis.org>

Steven Rostedt wrote:
> The recordmcount script is now robust enough not to process any sections
> but the .text section. But the gcc compiler still adds a call to mcount.
> 
> Note: The function mcount looks like:
> 
>   ENTRY(mcount)
> 	ret
>   END(mcount)
> 
> Which means the overhead is just a return.
> 
> This patch adds notrace to the init sections to not even bother calling
> mcount (which simply returns).

Sorry for a potentially dumb question (didn't follow all recent ftrace
developments), but doesn't this mean that code in such sections is now
invisible for all tracers, even with dynamic tracing disabled (in which
case they should cause no problem)? What if you *do* want to have such
functions in your trace as they may contribute to problem or give other
useful hints?

Jan

-- 
Siemens AG, Corporate Technology, CT SE 2
Corporate Competence Center Embedded Linux

  reply	other threads:[~2008-10-23 11:16 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-10-22 21:27 [PATCH 00/13 v2] ftrace: clean ups and fixes Steven Rostedt
2008-10-22 21:27 ` [PATCH 01/13 v2] ftrace: handle generic arch calls Steven Rostedt
2008-10-27 15:35   ` Ingo Molnar
2008-10-22 21:27 ` [PATCH 02/13 v2] ftrace: dynamic ftrace process only text section Steven Rostedt
2008-10-22 21:27 ` [PATCH 03/13 v2] ftrace: return error on failed modified text Steven Rostedt
2008-10-22 21:27 ` [PATCH 04/13 v2] ftrace: comment arch ftrace code Steven Rostedt
2008-10-22 21:27 ` [PATCH 05/13 v2] ftrace: use probe_kernel Steven Rostedt
2008-10-22 21:27 ` [PATCH 06/13 v2] ftrace: only have ftrace_kill atomic Steven Rostedt
2008-10-22 21:27 ` [PATCH 07/13 v2] ftrace: add ftrace warn on to disable ftrace Steven Rostedt
2008-10-22 21:27 ` [PATCH 08/13 v2] ftrace: do not trace init sections Steven Rostedt
2008-10-23 11:15   ` Jan Kiszka [this message]
2008-10-23 11:36     ` Steven Rostedt
2008-10-23 14:30       ` Jan Kiszka
2008-10-23 16:05         ` Steven Rostedt
2008-10-23 16:40           ` Ingo Molnar
2008-10-23 16:51             ` Steven Rostedt
2008-10-22 21:27 ` [PATCH 09/13 v2] ftrace: disable dynamic ftrace for all archs that use daemon Steven Rostedt
2008-10-22 21:27 ` [PATCH 10/13 v2] ftrace: remove daemon Steven Rostedt
2008-10-22 21:27 ` [PATCH 11/13 v2] ftrace: remove mcount set Steven Rostedt
2008-10-22 21:27 ` [PATCH 12/13 v2] ftrace: remove ftrace hash Steven Rostedt
2008-10-22 21:27 ` [PATCH 13/13 v2] ftrace: remove notrace from arch ftrace file Steven Rostedt
2008-10-23  9:29 ` [PATCH 00/13 v2] ftrace: clean ups and fixes Wenji Huang
2008-10-23 10:49   ` Steven Rostedt

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