linux-kernel - Re: [RFC][PATCH 0/4] ftrace: Use -mfentry when supported (this is for x86

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Message-ID: <4D5E5BCF.1040509@hitachi.com>
Date:	Fri, 18 Feb 2011 20:45:19 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Frederic Weisbecker <fweisbec@...il.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Andi Kleen <andi@...stfloor.org>,
	2nddept-manager@....hitachi.co.jp
Subject: Re: [RFC][PATCH 0/4] ftrace: Use -mfentry when supported (this is
 for x86_64 right now)

(2011/02/18 5:11), Steven Rostedt wrote:
> On Fri, 2011-02-18 at 01:07 +0900, Masami Hiramatsu wrote:
> 
>> I just thought that frequent stop-machine is not so good from the user's
>> POV. I agree that disabled probe ignoring the call is enough.
>> Maybe, it could be done with the similar mechanism of jump optimization.
> 
> I thought jump optimization still calls stop_machine too?

Yes, but now it does batch optimization.
Even if hundreds kprobes are registered separately, jump optimization
has been done in background with a stop_machine per every 256 probes.
(Until optimizing, kprobes can use breakpoints instead)

Thank you,

-- 
Masami HIRAMATSU
2nd Dept. Linux Technology Center
Hitachi, Ltd., Systems Development Laboratory
E-mail: masami.hiramatsu.pt@...achi.com
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