[PATCH v5 perf 0/1] perf: Sharing PMU counters across compatible events

[Song Liu]

Changes v4 -> v5:
  1. Rebase upon latest tip/perf/core.
  2. Remove prototype from v4 (2/2).

Changes v3 -> v4:
  1. In __perf_install_in_context() always reprogram ctx for cpu and cgroup
     events to make sure event duplications set up properly.
  2. Add a prototype (2/2) to show potential solution of sharing PMU among
     CPU events and task events.

Changes v2 -> v3:
  1. Simplified event_pmu_add() as Jiri Olsa suggested

Changes v1 -> v2:
  1. Fixed a bug reported by 0day kernel testing robot

This is to follow up earlier discussion on sharing hardware PMU counters
across compatible events:

  https://marc.info/?t=151213803600016
  https://marc.info/?t=152547569200001

This version limits PMU sharing to events within same ctx. As a result,
compatible events are not evaluated during task schedule. This vesion also
limits PMU sharing to hardware counting events. From our discussion with
internal users, this is sufficient for most cases.

This version introduces virtual master event. The virtual master event
does require careful handling. But it is makes the logic of event add/del
cleaner.

Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>

Song Liu (1):
  perf: Sharing PMU counters across compatible events

 include/linux/perf_event.h |  61 ++++++++
 kernel/events/core.c       | 294 ++++++++++++++++++++++++++++++++++---
 2 files changed, 332 insertions(+), 23 deletions(-)

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2.17.1