linux-kernel - Re: [PATCH -tip tracing/kprobes 0/9] tracing/kprobes, perf: perf probe and kprobe-tracer bugfixes

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Date:	Tue, 20 Oct 2009 20:05:57 -0400
From:	Masami Hiramatsu <mhiramat@...hat.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Frederic Weisbecker <fweisbec@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	lkml <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Mike Galbraith <efault@....de>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Christoph Hellwig <hch@...radead.org>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Jim Keniston <jkenisto@...ibm.com>,
	"Frank Ch. Eigler" <fche@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	systemtap <systemtap@...rces.redhat.com>,
	DLE <dle-develop@...ts.sourceforge.net>
Subject: Re: [PATCH -tip tracing/kprobes 0/9] tracing/kprobes, perf: perf
 	probe and kprobe-tracer bugfixes

Ingo Molnar wrote:
> * Masami Hiramatsu <mhiramat@...hat.com> wrote:
>> Masami Hiramatsu wrote:
>>> Ingo Molnar wrote:
>>>> For example you might want to probe the point within schedule that calls
>>>> switch_mm() - this could be done via:
>>>>
>>>>    perf probe schedule@...tch_mm
>>>>
>>>> Or the point where 'next' gets assigned? Sure, you dont need to even
>>>> open the editor, if you know the rough outline of the function you can
>>>> probe it via:
>>>>
>>>>    perf probe schedule@...xt ='
>>>>
>>>> Note that i was able to specify both probes without having opened an
>>>> editor - just based on the general knowledge of the scheduler.
>>>
>>> It may be useful for return probe too :-)
>>>
>>>  perf probe schedule@...urn
>>
>> Hmm, IMHO,
>>
>>>>    perf probe schedule@...tch_mm
>>
>> might be confused as 'probe schedule() called from switch_mm()'.
>>
>> BTW, there might be several local/inline functions which have
>> same name.
>> I think we'd better provide a syntax for solving this issue.
>> And current syntax uses @ for this purpose as below.
>>
>>  perf probe localfunc@...e
>>
>> Maybe, we still can use % for special matching,
>>
>>  perf probe schedule%switch_mm
>>
>> These can be combined with each other, as below.
>>
>>  perf probe schedule@...nel/sched.c%switch_mm
>>
>> Or, supporting lazy string pattern matching
>>  (reusing glob matching in ftrace?)
>>
>>  perf probe schedule:'switch_mm(*);'
>>
>> Just my thought.
> 
> I'm not attached to any particular form of syntax here (other than it 
> should be simple and obvious) - we can try and see how it works out.

OK, so I'll try to implement it and see how it works out:-)

-- 
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division

e-mail: mhiramat@...hat.com

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