linux-kernel - Re: [RFC PATCH -tip 2/9] ftrace/x86-64: support SAVE

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Date:	Wed, 30 May 2012 15:39:24 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	"Frank Ch. Eigler" <fche@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	yrl.pp-manager.tt@...achi.com
Subject: Re: [RFC PATCH -tip 2/9] ftrace/x86-64: support SAVE_REGS feature
 on x86-64

(2012/05/30 8:05), Steven Rostedt wrote:
> No! Please do not make ftrace save all regs for everyone. This is
> critical. This will slow down function tracing even more. We do not need
> to save all regs for every function call, unless it is asked for.

Indeed, I have just removed your save_regs dynamic selector code,
because I'd like to make this series as simple as possible
for review.

> It should only save all regs if the ftrace_ops that is registered asked
> for it. I had code that actually does that. I can merge your patches
> with them if you would like.

Yes, I'd like :)

BTW, that code which dynamically selects trace_caller on your
ftrace-v2 tree, seems to be an uncompleted work. Would you
already have done it?

Thank you,

-- 
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@...achi.com
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