Hi
I am trying to use perf with event grouping to profile Java apps.
My kernel is 3.16.1-1.el6.elrepo.x86_64
perf version 3.16.1-1.el6.elrepo.x86_64
The Java app I use is hadoop TaskTracker, which spawns multiple child JVMs.
There seems to be something wrong with event group, since very few
samples were collected if I use more than one event in a group.
The following shows an example
I used
perf record -e '{instructions}:S' -c 100000 [TaskTracker command]
This one works fine and it collects a reasonable amount of samples and
several threads are sampled.
However, the following command does not work.
perf record -e '{instructions,cycles}:S' -c 100000 [TaskTracker command]
Less than 1000 samples were collected and only one thread was sampled
If I don't use :S to read samples, the sample counts are reasonable,
but the event grouping is gone. (both events were sampled, no leader
event.)
perf record -e '{instructions,cycles}' -c 100000 [TaskTracker command]
I tested single-threaded app, such as SPEC CPU.
Everything works fine. The event grouping works fine, so as the :S flag.
However, the Java app that I tested does not.
Please let me know if any suggestions on this issue.
Thanks.
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