From: Ian Rogers <irogers@google.com>
To: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
linux-kernel@vger.kernel.org, Andi Kleen <ak@linux.intel.com>,
Jin Yao <yao.jin@linux.intel.com>,
John Garry <john.garry@huawei.com>, Paul Clarke <pc@us.ibm.com>,
kajoljain <kjain@linux.ibm.com>,
linux-perf-users@vger.kernel.org
Cc: Stephane Eranian <eranian@google.com>,
Sandeep Dasgupta <sdasgup@google.com>,
Ian Rogers <irogers@google.com>
Subject: [PATCH v9 13/13] perf metric: Avoid events for an 'if' constant result
Date: Thu, 23 Sep 2021 00:46:16 -0700 [thread overview]
Message-ID: <20210923074616.674826-14-irogers@google.com> (raw)
In-Reply-To: <20210923074616.674826-1-irogers@google.com>
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>
---
tools/perf/tests/expr.c | 7 +++++++
tools/perf/util/expr.y | 10 ++++++++++
2 files changed, 17 insertions(+)
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
--
2.33.0.464.g1972c5931b-goog
next prev parent reply other threads:[~2021-09-23 7:47 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-23 7:46 [PATCH v9 00/13] Don't compute events that won't be used in a metric Ian Rogers
2021-09-23 7:46 ` [PATCH v9 01/13] perf metric: Restructure struct expr_parse_ctx Ian Rogers
2021-09-23 7:46 ` [PATCH v9 02/13] perf metric: Use NAN for missing event IDs Ian Rogers
2021-09-23 7:46 ` [PATCH v9 03/13] perf expr: Remove unused headers and inline d_ratio Ian Rogers
2021-09-23 7:46 ` [PATCH v9 04/13] perf expr: Separate token declataion from type Ian Rogers
2021-09-23 7:46 ` [PATCH v9 05/13] perf expr: Use macros for operators Ian Rogers
2021-09-23 7:46 ` [PATCH v9 06/13] perf expr: Move actions to the left Ian Rogers
2021-09-23 7:46 ` [PATCH v9 07/13] perf metric: Rename expr__find_other Ian Rogers
2021-09-23 7:46 ` [PATCH v9 08/13] perf metric: Add utilities to work on ids map Ian Rogers
2021-09-23 7:46 ` [PATCH v9 09/13] perf metric: Allow metrics with no events Ian Rogers
2021-09-23 7:46 ` [PATCH v9 10/13] perf expr: Merge find_ids and regular parsing Ian Rogers
2021-09-28 20:56 ` Jiri Olsa
2021-09-28 21:20 ` Ian Rogers
2021-09-23 7:46 ` [PATCH v9 11/13] perf expr: Propagate constants for binary operations Ian Rogers
2021-09-23 7:46 ` [PATCH v9 12/13] perf metric: Don't compute unused events Ian Rogers
2021-09-23 7:46 ` Ian Rogers [this message]
2021-09-29 5:35 ` [PATCH v9 00/13] Don't compute events that won't be used in a metric Jiri Olsa
2021-09-29 15:19 ` John Garry
2021-09-29 16:09 ` Ian Rogers
2021-09-29 16:51 ` Arnaldo Carvalho de Melo
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