linux-kernel - Re: [RFC PATCH -tip 0/9]ftrace, kprobes: Ftrace-based kprobe optimization

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Message-ID: <4FC5C55E.9000909@hitachi.com>
Date:	Wed, 30 May 2012 15:59:42 +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  0/9]ftrace, kprobes: Ftrace-based kprobe optimization

(2012/05/30 7:45), Steven Rostedt wrote:
> On Tue, 2012-05-29 at 21:48 +0900, Masami Hiramatsu wrote:
> 
>> Also, this makes all __kprobes functions "notrace", because
>> some of those functions are considered as to be called from
>> kprobes handler which is called from function tracer.
>> I think that is another discussion point. Perhaps, we need
>> to introduce another tag which means "don't put kprobe on
>> this function" instead of __kprobes and apply that.
> 
> Actually, instead, we can force kprobes to have all "__kprobes"
> functions added to its 'notrace' ftrace_ops. This will just keep kprobes
> from function tracing these, as I find myself tracing functions marked
> by kprobes quite a bit.

Hmm, I'm not so sure how the notrace and filter works.
What happens if I set a foo function-entry on filter
and keep notrace empty?
 - only foo's nop is replaced with call?
 - or all functions including foo is traced?

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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