linux-kernel - Confusing help regarding single-depth WCHAN output

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Message-ID: <20090809151458.GA32444@ime.usp.br>
Date:	Sun, 9 Aug 2009 12:14:58 -0300
From:	Rogério Brito <rbrito@....usp.br>
To:	linux-kernel@...r.kernel.org
Subject: Confusing help regarding single-depth WCHAN output

Hi.

I noticed this some releases ago, but only now I was perusing the kernel
with a little more attention and got very curious. When doing a "make
menuconfig" on an amd64 system, I get the following message:

,----
| Single-depth WCHAN output
| CONFIG_SCHED_OMIT_FRAME_POINTER:
| 
|  Calculate simpler /proc/<PID>/wchan values. If this option
|  is disabled then wchan values will recurse back to the
|  caller function. This provides more accurate wchan values,
|  at the expense of slightly more scheduling overhead.
| 
|  If in doubt, say "Y".
| 
|  Symbol: SCHED_OMIT_FRAME_POINTER [=y]
|  Prompt: Single-depth WCHAN output
|    Defined at arch/x86/Kconfig:441
|    Depends on: X86
|    Location:
|      -> Processor type and features
`----

Is the WCHAN option related to omitting a frame pointer? If yes, how
could this be written in a more detailed way?

Thanks for any comments, Rogério Brito.

-- 
Rogério Brito : rbrito@...ckenzie,ime.usp}.br : GPG key 1024D/7C2CAEB8
http://www.ime.usp.br/~rbrito : http://meusite.mackenzie.com.br/rbrito
Projects: algorithms.berlios.de : lame.sf.net : vrms.alioth.debian.org
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