linux-kernel - Re: Re: [PATCH] perf/probe: Provide perf interface for uprobes

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Date:	Thu, 12 Apr 2012 12:27:47 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Arnaldo Carvalho de Melo <acme@...radead.org>
Cc:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Jim Keniston <jkenisto@...ux.vnet.ibm.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux-mm <linux-mm@...ck.org>, Oleg Nesterov <oleg@...hat.com>,
	Andi Kleen <andi@...stfloor.org>,
	Christoph Hellwig <hch@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Anton Arapov <anton@...hat.com>
Subject: Re: Re: [PATCH] perf/probe: Provide perf interface for uprobes

(2012/04/12 3:17), Arnaldo Carvalho de Melo wrote:
> Em Wed, Apr 11, 2012 at 10:42:25PM +0530, Srikar Dronamraju escreveu:
>> * Arnaldo Carvalho de Melo <acme@...radead.org> [2012-04-11 11:49:18]:
>>> Em Wed, Apr 11, 2012 at 07:27:42PM +0530, Srikar Dronamraju escreveu:
>>>> From: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
>>>>
>>>> - Enhances perf to probe user space executables and libraries.
>>>> - Enhances -F/--funcs option of "perf probe" to list possible probe points in
>>>>   an executable file or library.
>>>> - Documents userspace probing support in perf.
>>>>
>>>> [ Probing a function in the executable using function name  ]
>>>> perf probe -x /bin/zsh zfree
>>>
>>> Can we avoid the need for -x? I.e. we could figure out it is userspace
>>> and act accordingly.
>>
>> To list the functions in the module ipv6, we use "perf probe -F -m ipv6"
>> So I used the same logic to use -x for specifying executables.
>>
>> This is in agreement with probepoint addition where without any
>> additional options would mean kernel probepoint; m option would mean
>> module and x option would mean user space executable. 
>>
>> However if you still think we should change, do let me know.
> 
> Yeah, if one needs to disambiguate, sure, use these keywords, but for
> things like:
> 
> $ perf probe /lib/libc.so.6 malloc
> 
> I think it is easy to figure out it is userspace. I.e. some regex would
> figure it out.

That's interessting to me too. Maybe it is also useful syntax for
module specifying too.

e.g.
  perf probe -m kvm kvm_timer_fn

can be

  perf probe kvm.ko kvm_timer_fn

(.ko is required) or if unloaded

  perf probe /lib/modules/XXX/kernel/virt/kvm.ko kvm_timer_fn

Thanks!

-- 
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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