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

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Message-ID: <20120412140751.GM16257@infradead.org>
Date:	Thu, 12 Apr 2012 11:07:51 -0300
From:	Arnaldo Carvalho de Melo <acme@...radead.org>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
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

Em Thu, Apr 12, 2012 at 12:27:47PM +0900, Masami Hiramatsu escreveu:
> > * Arnaldo Carvalho de Melo <acme@...radead.org> [2012-04-11 11:49:18]:
> > 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

	It may not even be required, since we can check in /proc/modules
if "kvm" is there and as well if it has a function named "kvm_timer_fn".

	Also probably there is no library or binary on the current
directory with such a name :-)

	Likewise, if we do:

 $ perf probe libc-2.12.so malloc

	It should just figure out it is the /lib64/libc-2.12.so

	Heck, even:

 $ perf probe libc malloc

	Makes it even easier to use.

	Its just when one asks for something that has ambiguities that
the tool should ask the user to be a bit more precise to remove such
ambiguity.

	After all...

[acme@...dy linux]$ locate libc-2.12.so
/home/acme/.debug/lib64/libc-2.12.so
/home/acme/.debug/lib64/libc-2.12.so/293f8b6f5e6cea240d1bb0b47ec269ee91f31673
/home/acme/.debug/lib64/libc-2.12.so/5a7fad9dfcbb67af098a258bc2a20137cc954424
/lib64/libc-2.12.so
/usr/lib/debug/lib64/libc-2.12.so.debug
[acme@...dy linux]$

	Only /lib64/libc-2.12.so is on the ld library path :-)

	And after people really start depending on this tool for day to
day use, they may do like me:

[root@...dy ~]# alias probe="perf probe"
[root@...dy ~]# probe -F | grep skb_queue
skb_queue_head
skb_queue_purge
skb_queue_tail
[root@...dy ~]#

	Which gets it to the shortest possible form:

	$ probe libc malloc

	:-)

	Git has this nice feature that is on the same line of making
things easier for the user:

[acme@...dy linux]$ git fack
git: 'fack' is not a git command. See 'git --help'.

Did you mean this?
	fsck
[acme@...dy linux]$

	Hell, yes, fsck is what I meant! :-)

- Arnaldo
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