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 08:51:51 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Masami Hiramatsu <mhiramat@...hat.com>
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


* 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.

	Ingo
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