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Date: Sat, 20 Jun 2009 18:24:06 -0400 (EDT)
From: Steven Rostedt <rostedt@goodmis.org>
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To: Ingo Molnar <mingo@elte.hu>
cc: linux-kernel@vger.kernel.org, Andrew Morton <akpm@linux-foundation.org>,
       Frederic Weisbecker <fweisbec@gmail.com>
Subject: Re: [PATCH 1/2] function-graph: disable when both x86_32 and optimize
 for size are configured
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On Sat, 20 Jun 2009, Ingo Molnar wrote:

> 
> * Steven Rostedt <rostedt@goodmis.org> wrote:
> 
> > diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
> > index 4a13e5a..1eac852 100644
> > --- a/kernel/trace/Kconfig
> > +++ b/kernel/trace/Kconfig
> > @@ -121,6 +121,7 @@ config FUNCTION_GRAPH_TRACER
> >  	bool "Kernel Function Graph Tracer"
> >  	depends on HAVE_FUNCTION_GRAPH_TRACER
> >  	depends on FUNCTION_TRACER
> > +	depends on !X86_32 || !CC_OPTIMIZE_FOR_SIZE
> >  	default y
> 
> Hm, nice fix, but this is a quite nasty constraint - distros like to 
> enable CC_OPTIMIZE_FOR_SIZE as it neatly trims the kernel's size by 
> about 30%.
> 
> Just in case you have not checked yet: is there no way to turn off 
> the specific gcc optimization that causes this? Or is it -Os itself 
> that does this optimization?

It seems to me that -Os causes it for i386. I did a make V=1 to capture 
how the files in question were being compiled, and tried various disabling 
of flags. -Os was the only one to make a difference. :-(

-- Steve