linux-kernel - Re: [PATCH 1/2] function-graph: disable when both x86

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Message-ID: <20090620162513.GD32377@elte.hu>
Date:	Sat, 20 Jun 2009 18:25:13 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCH 1/2] function-graph: disable when both x86_32 and
	optimize for size are configured


* Steven Rostedt <rostedt@...dmis.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?

	Ingo
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