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| author |   Ian Rogers <irogers@google.com> | 2021-09-23 00:46:16 -0700 |
|---|---|---|
| committer |   Arnaldo Carvalho de Melo <acme@redhat.com> | 2021-09-29 13:51:04 -0300 |
| commit | 94886961e324d5b6bae8e206b227c6eeb0f22c2c (patch) | |
| tree | 0f2b6a404a06e0f5bcadcf6bcb8643cf2bf7cd9f | |
| parent | perf metric: Don't compute unused events (diff) | |
| download | linux-dev-94886961e324d5b6bae8e206b227c6eeb0f22c2c.tar.xz linux-dev-94886961e324d5b6bae8e206b227c6eeb0f22c2c.zip | |
perf metric: Avoid events for an 'if' constant result
For a metric like:
CONST if expr else CONST
if the values of CONST are identical then expr doesn't need evaluating,
and events, in order to compute a result.
Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: John Garry <john.garry@huawei.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Clarke <pc@us.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sandeep Dasgupta <sdasgup@google.com>
Cc: Stephane Eranian <eranian@google.com>
Link: https://lore.kernel.org/r/20210923074616.674826-14-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
| -rw-r--r-- | tools/perf/tests/expr.c | 7 | ||||
| -rw-r--r-- | tools/perf/util/expr.y | 10 |
2 files changed, 17 insertions, 0 deletions
diff --git a/tools/perf/tests/expr.c b/tools/perf/tests/expr.c index 287989321d2a..f1d8411fce12 100644 --- a/tools/perf/tests/expr.c +++ b/tools/perf/tests/expr.c @@ -143,6 +143,13 @@ int test__expr(struct test *t __maybe_unused, int subtest __maybe_unused) smt_on() ? "EVENT1" : "EVENT2", (void **)&val_ptr)); + /* The expression is a constant 1.0 without needing to evaluate EVENT1. */ + expr__ctx_clear(ctx); + TEST_ASSERT_VAL("find ids", + expr__find_ids("1.0 if EVENT1 > 100.0 else 1.0", + NULL, ctx, 0) == 0); + TEST_ASSERT_VAL("find ids", hashmap__size(ctx->ids) == 0); + expr__ctx_free(ctx); return 0; diff --git a/tools/perf/util/expr.y b/tools/perf/util/expr.y index 5b878f044f22..ba7d3b667fcb 100644 --- a/tools/perf/util/expr.y +++ b/tools/perf/util/expr.y @@ -142,6 +142,16 @@ if_expr: expr IF expr ELSE expr $$.ids = $1.ids; ids__free($3.ids); ids__free($5.ids); + } else if ($1.val == $5.val) { + /* + * LHS == RHS, so both are an identical constant. No need to + * evaluate any events. + */ + $$.val = $1.val; + $$.ids = NULL; + ids__free($1.ids); + ids__free($3.ids); + ids__free($5.ids); } else { /* * Value is either the LHS or RHS and we need the IF expression |