[USDT] perf_events USDT help wanted #61

I noticed that nodejs/diagnostics doesn't seem to cover the Linux perf_events USDT work, which originated with Hemant Kumar, has been updated by Masami Hiramatsu, and now getting pushed by Arnaldo Carvalho de Melo. This is Linux mainline support for USDT probes.

Eg, as part of the patchset that was just pulled by Ingo, and will hopefully be then pulled by Linus for the 4.7 release:

  # perf buildid-cache --add /lib/libc-2.17.so
  # perf probe --cache --list | head -n 5
  /usr/lib/libc-2.17.so (a6fb821bdf53660eb2c29f778757aef294d3d392):
  sdt_libc:setjmp=setjmp
  sdt_libc:longjmp=longjmp
  sdt_libc:longjmp_target=longjmp_target
  sdt_libc:memory_heap_new=memory_heap_new
  # perf probe -x /usr/lib/libc-2.17.so \
    -a sdt_libc:memory_heap_new=memory_heap_new
  Added new event:
    sdt_libc:memory_heap_new (on memory_heap_new
   in /usr/lib/libc-2.17.so)
  You can now use it in all perf tools, such as:

          perf record -e sdt_libc:memory_heap_new -aR sleep 1

  # perf probe -l
    sdt_libc:memory_heap_new (on new_heap+183 in /usr/lib/libc-2.17.so)

That example shows the libc USDT probe.

There's more work to do: handling arguments, and more BPF support for in-kernel aggregations. Something that's slowing the process is the lack of help: people testing and commenting on these patchsets. I've done some myself, but help is desired.

nodejs/diagnostics should at least refer to this work, come up with examples for the Node.js probes, and hopefully encourage others to contribute. You can currently search lkml for "SDT" patchsets from either Masami Hiramatsu or Arnaldo Carvalho de Melo, usually marked "perf/core".

This is Linux mainline.