linux-kernel - Re: [PATCH 2/3] ftrace/x86: Add support for C version of recordmcount

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Date:	Fri, 15 Oct 2010 04:50:47 +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>,
	linux-arch@...r.kernel.org, Michal Marek <mmarek@...e.cz>,
	linux-kbuild@...r.kernel.org, John Reiser <jreiser@...wagon.com>
Subject: Re: [PATCH 2/3] ftrace/x86: Add support for C version of recordmcount


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

> From: Steven Rostedt <srostedt@...hat.com>
> 
> This patch adds the support for the C version of recordmcount and
> compile times show ~ 12% improvement.

I reported this recordmcount performance problem 2 years ago. Better 
later than never i guess.

> +ifdef CONFIG_DYNAMIC_FTRACE
> +	ifdef CONFIG_HAVE_C_MCOUNT_RECORD
> +		BUILD_C_RECORDMCOUNT := y
> +		export BUILD_C_RECORDMCOUNT

> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -33,6 +33,7 @@ config X86
>  	select HAVE_KRETPROBES
>  	select HAVE_OPTPROBES
>  	select HAVE_FTRACE_MCOUNT_RECORD
> +	select HAVE_C_MCOUNT_RECORD

The naming is inconsistent here - it should be HAVE_C_RECORDMCOUNT, like 
the build variable has, and like the utility is called. If we are going 
to add this flag to most architectures we should name it consistently.

Thanks,

	Ingo
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