On 04/13/2017 03:38 PM, Milosz Tanski wrote:
On Thu, Apr 13, 2017 at 2:02 PM, Mohamad Gebai <mgebai@xxxxxxxx> wrote:
On 04/13/2017 01:20 PM, Mark Nelson wrote:
Nice! I will give it a try and see how it goes. Specifically I want to
compare it to what I ended up working on yesterday. After the meeting I
ended up doing major surgery on an existing gdb based wallclock profiler and
modified it to a) work b) be thread aware c) print inverse call-graphs. The
code is still pretty rough but you can see it here:
https://github.com/markhpc/gdbprof
Very neat, thank you for this. Please let me know what happens, I'm
interested to see which tool ends up working best for this use case. Also,
could you share some information about what you're trying to find out?
If I'm not mistaken, there's work being done to add the call stack of a
process within the context of LTTng events. That way we could have this
information when a process blocks in sys_futex.
PS: found it, it's still in RFC -
https://lists.lttng.org/pipermail/lttng-dev/2017-March/026985.html
You can also use perf's syscall tracepoints to capture the
syscalls:sys_enter_futex event. This way you get contended mutex. The
nice thing about it is all the normal perf tools apply, so you can see
source annotation, frequency (hot points) and also examine the
callgraph of the hot points.
Hi Milosz,
Do you know of any examples showing this technique? I've suspected
there was a way to do this (and similar things) with perf, but always
ran into roadblocks that made it not work. Potentially one of those
roadblocks might have been errors on my part. ;)
Mark
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