[PATCH] perf test: Make metric testing more robust.

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>,
	John Garry <john.garry@huawei.com>,
	Kajol Jain <kjain@linux.ibm.com>,
	linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org
Cc: eranian@google.com, Ian Rogers <irogers@google.com>
Subject: [PATCH] perf test: Make metric testing more robust.
Date: Wed,  4 Aug 2021 00:25:47 -0700	[thread overview]
Message-ID: <20210804072547.1728924-1-irogers@google.com> (raw)

When testing metric expressions we fake counter values from 1 going
upward. For some metrics this can yield negative values that are clipped
to zero, and then cause divide by zero failures. A workaround for this
case is to try a second time with counter values going in the opposite
direction.

This case was seen in a metric like:
  event1 / max(event2 - event3, 0)

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/tests/pmu-events.c | 32 ++++++++++++++++++++++++++------
 1 file changed, 26 insertions(+), 6 deletions(-)

diff --git a/tools/perf/tests/pmu-events.c b/tools/perf/tests/pmu-events.c
index b8aff8fb50d8..6c1cd58605c1 100644
--- a/tools/perf/tests/pmu-events.c
+++ b/tools/perf/tests/pmu-events.c
@@ -600,8 +600,18 @@ static int test_parsing(void)
 			}
 
 			if (expr__parse(&result, &ctx, pe->metric_expr, 0)) {
-				expr_failure("Parse failed", map, pe);
-				ret++;
+				/*
+				 * Parsing failed, make numbers go from large to
+				 * small which can resolve divide by zero
+				 * issues.
+				 */
+				k = 1024;
+				hashmap__for_each_entry((&ctx.ids), cur, bkt)
+					expr__add_id_val(&ctx, strdup(cur->key), k--);
+				if (expr__parse(&result, &ctx, pe->metric_expr, 0)) {
+					expr_failure("Parse failed", map, pe);
+					ret++;
+				}
 			}
 			expr__ctx_clear(&ctx);
 		}
@@ -656,10 +666,20 @@ static int metric_parse_fake(const char *str)
 		}
 	}
 
-	if (expr__parse(&result, &ctx, str, 0))
-		pr_err("expr__parse failed\n");
-	else
-		ret = 0;
+	ret = 0;
+	if (expr__parse(&result, &ctx, str, 0)) {
+		/*
+		 * Parsing failed, make numbers go from large to small which can
+		 * resolve divide by zero issues.
+		 */
+		i = 1024;
+		hashmap__for_each_entry((&ctx.ids), cur, bkt)
+			expr__add_id_val(&ctx, strdup(cur->key), i--);
+		if (expr__parse(&result, &ctx, str, 0)) {
+			pr_err("expr__parse failed\n");
+			ret = -1;
+		}
+	}
 
 out:
 	expr__ctx_clear(&ctx);
-- 
2.32.0.554.ge1b32706d8-goog

