linux-kernel - Re: [PATCH v4 3.0-rc2-tip 20/22] 20: perf: perf interface for uprobes

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Message-ID: <4DEE832D.3010901@redhat.com>
Date:	Tue, 07 Jun 2011 12:59:41 -0700
From:	Josh Stone <jistone@...hat.com>
To:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
CC:	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...e.hu>,
	Steven Rostedt <rostedt@...dmis.org>,
	Linux-mm <linux-mm@...ck.org>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Hugh Dickins <hughd@...gle.com>,
	Christoph Hellwig <hch@...radead.org>,
	Andi Kleen <andi@...stfloor.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Jonathan Corbet <corbet@....net>,
	Oleg Nesterov <oleg@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jim Keniston <jkenisto@...ux.vnet.ibm.com>,
	Roland McGrath <roland@...k.frob.com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 3.0-rc2-tip 20/22] 20: perf: perf interface for uprobes

On 06/07/2011 06:02 AM, Srikar Dronamraju wrote:
> Enhances perf probe to user space executables and libraries.
> Provides very basic support for uprobes.

Hi Srikar,

This seems to have an issue with multiple active uprobes, whereas the v3
patchset handled this fine.  I haven't tracked down the exact code
difference yet, but here's an example transcript of what I'm seeing:

# perf probe -l
  probe_zsh:main       (on /bin/zsh:0x000000000000e3f0)
  probe_zsh:zalloc     (on /bin/zsh:0x0000000000051120)
  probe_zsh:zfree      (on /bin/zsh:0x0000000000051c70)
# perf stat -e probe_zsh:main zsh -c true

 Performance counter stats for 'zsh -c true':

                 1 probe_zsh:main

       0.029387785 seconds time elapsed

# perf stat -e probe_zsh:zalloc zsh -c true

 Performance counter stats for 'zsh -c true':

               605 probe_zsh:zalloc

       0.043836002 seconds time elapsed

# perf stat -e probe_zsh:zfree zsh -c true

 Performance counter stats for 'zsh -c true':

                36 probe_zsh:zfree

       0.029445890 seconds time elapsed

# perf stat -e probe_zsh:* zsh -c true

 Performance counter stats for 'zsh -c true':

                 0 probe_zsh:zalloc
                 1 probe_zsh:main
                 0 probe_zsh:zfree

       0.030912587 seconds time elapsed

# perf stat -e probe_zsh:z* zsh -c true

 Performance counter stats for 'zsh -c true':

               605 probe_zsh:zalloc
                 0 probe_zsh:zfree

       0.043774671 seconds time elapsed


It seems like among the selected probes, only one with the lowest offset
ever gets hit.  Any ideas?

Thanks,
Josh
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