Messages in this thread | | | Date | Thu, 23 Sep 2021 00:46:03 -0700 | Subject | [PATCH v9 00/13] Don't compute events that won't be used in a metric. | From | Ian Rogers <> |
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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.
v9. adds a missing memory allocation failure check in the pmu-metrics test. A memory allocation failure in union returns NULL. Some parser debug on IDs is removed. "Modify code layout" is broken apart into 3 changes. "Don't compute unused events" is broken apart into 4 changes with the tests merged into the change that adds the corresponding optimization. This is trying to address feedback from Jiri Olsa <jolsa@redhat.com>. The unmodified patches have Reviewed-by: Andi Kleen <ak@linux.intel.com> added, although the overall patch set is largely the same as v8 which was fully reviewed-by.
v8. rebases, adds an ability to compute metrics with no events and further breaks apart the "Don't compute unused events" part of the change as requested by Jiri Olsa <jolsa@redhat.com>.
v7. fixes the fix to be in the correct patch.
v6. rebases and fixes issues raised by Namhyung Kim <namhyung@kernel.org>, a memory leak and a function comment.
v5. uses macros to reduce boiler plate in patch 5/5 as suggested by Andi Kleen <ak@linux.intel.com>.
v4. reduces references to BOTTOM/NAN in patch 5/5 by using utility functions. It improves comments and fixes an unnecessary union in a peephole optimization.
v3. fixes an assignment in patch 2/5. In patch 5/5 additional comments are added and useless frees are replaced by asserts. A new peephole optimization is added for the case CONST IF expr ELSE CONST, where the the constants are identical, as we don't need to evaluate the IF condition.
v2. is a rebase.
Ian Rogers (13): perf metric: Restructure struct expr_parse_ctx. perf metric: Use NAN for missing event IDs. perf expr: Remove unused headers and inline d_ratio perf expr: Separate token declataion from type perf expr: Use macros for operators perf expr: Move actions to the left. perf metric: Rename expr__find_other. perf metric: Add utilities to work on ids map. perf metric: Allow metrics with no events perf expr: Merge find_ids and regular parsing perf expr: Propagate constants for binary operations perf metric: Don't compute unused events perf metric: Avoid events for an 'if' constant result
tools/perf/tests/expr.c | 160 ++++++++++++----- tools/perf/tests/pmu-events.c | 54 +++--- tools/perf/util/expr.c | 121 +++++++++++-- tools/perf/util/expr.h | 20 ++- tools/perf/util/expr.l | 9 - tools/perf/util/expr.y | 325 +++++++++++++++++++++++++--------- tools/perf/util/metricgroup.c | 145 ++++++++------- tools/perf/util/stat-shadow.c | 54 +++--- 8 files changed, 620 insertions(+), 268 deletions(-)
-- 2.33.0.464.g1972c5931b-goog
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