Re: [PATCH v9 00/13] Don't compute events that won't be used in a metric.

Jiri Olsa
2021-09-29T05:35:33Z

On Thu, Sep 23, 2021 at 12:46:03AM -0700, Ian Rogers wrote:
> 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.

Acked-by: Jiri Olsa <jolsa@redhat.com>

thanks,
jirka

>
> 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
>