[RFC 0/5] perf: Allow leader sampling on inherited events

[Jiri Olsa]

hi,
Jen-Cheng(Tommy) Huang reported the leader sampling not working
on children processes:
  http://www.mail-archive.com/linux-perf-users@xxxxxxxxxxxxxxx/msg01644.html

The leader sampling (example below) lets the group leader event (cycles)
do the sampling and reads the rest of the group (cache-misses) via
PERF_FORMAT_GROUP format.

Example:
  $ perf record -e '{cycles,cache-misses}:S' <workload>
  $ perf report --group

  The perf report --group allows to see all events group
  data in single view.

The reason for leader sampling being switched off for inherited
events, is that the kernel does no allow PERF_FORMAT_GROUP format
on inherited events (which is used by leader sampling).

I switched on the PERF_FORMAT_GROUP format for inherited events
with few other fixies in patches:
  perf: Deny optimized switch for events read by PERF_SAMPLE_READ
  perf: Allow PERF_FORMAT_GROUP format on inherited events

And I fixed perf tool code to be able to process data from
children processes.

Anyway, I might have missed some other reason why this was
never switched on in kernel, so sending this as RFC.

thanks for comments,
jirka


Reported-by: Jen-Cheng(Tommy) Huang <tommy24@xxxxxxxxxx>
Cc: Andi Kleen <andi@xxxxxxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Corey Ashford <cjashfor@xxxxxxxxxxxxxxxxxx>
Cc: David Ahern <dsahern@xxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Jen-Cheng(Tommy) Huang <tommy24@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Stephane Eranian <eranian@xxxxxxxxxx>
Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
---
Jiri Olsa (5):
      perf: Deny optimized switch for events read by PERF_SAMPLE_READ
      perf: Allow PERF_FORMAT_GROUP format on inherited events
      perf tools: Add support to traverse xyarrays
      perf tools: Add hash of periods for struct perf_sample_id
      perf tools: Allow PERF_FORMAT_GROUP for inherited events

 kernel/events/core.c            | 25 ++++++++++++++-----------
 tools/perf/Makefile.perf        |  1 +
 tools/perf/tests/builtin-test.c |  4 ++++
 tools/perf/tests/tests.h        |  1 +
 tools/perf/tests/xyarray.c      | 33 +++++++++++++++++++++++++++++++++
 tools/perf/util/evsel.c         | 17 ++++++++++++++---
 tools/perf/util/evsel.h         |  5 ++++-
 tools/perf/util/session.c       | 93 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++------
 tools/perf/util/xyarray.c       |  4 +++-
 tools/perf/util/xyarray.h       |  6 ++++++
 10 files changed, 167 insertions(+), 22 deletions(-)
 create mode 100644 tools/perf/tests/xyarray.c
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