[PATCH v2 0/5] Don't compute events that won't be used in a metric.

Ian Rogers
2020-11-18T05:04:01Z

For a metric like:
EVENT1 if #smt_on else EVENT2

currently EVENT1 and EVENT2 will be measured and then when the metric
is reported EVENT1 or EVENT2 will be printed depending on the value
from smt_on() during the expr parsing. Computing both events is
unnecessary and can lead to multiplexing as discussed in this thread:
https://lore.kernel.org/lkml/20201110100346.2527031-1-irogers@google.com/

This change modifies expression parsing so that constants are
considered when building the set of ids (events) and only events not
contributing to a constant value are measured.

v2. is a rebase.

Ian Rogers (5):
perf metric: Restructure struct expr_parse_ctx.
perf metric: Use NAN for missing event IDs.
perf metric: Rename expr__find_other.
perf metric: Add utilities to work on ids map.
perf metric: Don't compute unused events.

tools/perf/tests/expr.c | 148 ++++++++++-----
tools/perf/tests/pmu-events.c | 42 +++--
tools/perf/util/expr.c | 136 ++++++++++++--
tools/perf/util/expr.h | 17 +-
tools/perf/util/expr.l | 9 -
tools/perf/util/expr.y | 343 +++++++++++++++++++++++++++-------
tools/perf/util/metricgroup.c | 44 +++--
tools/perf/util/stat-shadow.c | 54 ++++--
8 files changed, 586 insertions(+), 207 deletions(-)

--
2.29.2.299.gdc1121823c-goog