Messages in this thread | | | Date | Tue, 17 Jan 2012 13:21:33 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH v9 3.2 7/9] tracing: uprobes trace_event interface |
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Have you tried to use 'perf probe' to achieve any useful instrumentation on a real app?
I just tried out the 'glibc:free' usecase and it's barely usable.
Firstly, the recording very frequently produces overruns:
$ perf record -e probe_libc:free -aR sleep 1 [ perf record: Woken up 169 times to write data ] [ perf record: Captured and wrote 89.674 MB perf.data (~3917919 samples) ] Warning:Processed 1349133 events and lost 1 chunks!
Using -m 4096 made it work better.
Adding -g for call-graph profiling caused 'perf report' to lock up:
perf record -m 4096 -e probe_libc:free -agR sleep 1 perf report [ loops forever ]
I've sent a testcase to Arnaldo separately. Note that perf report --stdio appears to work.
Regular '-e cycles -g' works fine, so this is a uprobes specific bug.
Thanks,
Ingo
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