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

Josh Stone
2011-06-07T20:00:20Z

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