[RFC PATCH v1 0/3] Retirement latency perf stat support

[Ian Rogers]

Support 'R' as a retirement latency modifier on events. When present
the evsel will fork perf record and perf report commands, parsing the
perf report output as the count value. The intent is to do something
similar to Weilin's series:
https://lore.kernel.org/lkml/20240402214436.1409476-1-weilin.wang@xxxxxxxxx/

While the 'R' and the retirement latency are Intel specific, in the
future I can imagine more evsel like commands that require child
processes. We can make the logic more generic at that point.

The code is untested on hardware that supports retirement latency, and
with metrics with retirement latency in them. The record is also of
sleep and various things need tweaking but I think v1 is good enough
for people to give input.

The first patch stops opening a dummy event for tool events. I came
across this while looking into the issue and we can likely just pick
it first. I kept it in the series for cleanliness sake.

The code has benefitted greatly from Weilin's work and Namhyung's
great review input.

Ian Rogers (3):
  perf evsel: Don't open tool events
  perf parse-events: Add a retirement latency modifier
  perf evsel: Add retirement latency event support

 tools/perf/util/evsel.c        | 186 ++++++++++++++++++++++++++++++++-
 tools/perf/util/evsel.h        |   4 +
 tools/perf/util/parse-events.c |   2 +
 tools/perf/util/parse-events.h |   1 +
 tools/perf/util/parse-events.l |   3 +-
 5 files changed, 192 insertions(+), 4 deletions(-)

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2.44.0.769.g3c40516874-goog