Commit 87a73bdc authored Dec 23, 2021 by Ian Rogers Committed by Arnaldo Carvalho de Melo Feb 15, 2022

perf test: Make metric testing more robust



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.

Such clipping is questionable but may be a result of tools automatically
generating metrics. 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)
But it may also happen in more sensible metrics like:
  event1 / (event2 + event3 - 1 - event4)

Reviewed-by: John Garry <john.garry@huawei.com>
Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: https://lore.kernel.org/r/20211223185622.3435128-1-irogers@google.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

parent aca8af3c

tools/perf/tests/pmu-events.c

+26 −6

Original line number	Diff line number	Diff line
		@@ -993,12 +993,22 @@ static int test__parsing(struct test_suite *test __maybe_unused,
		free(metric);
		}

		if (expr__parse(&result, ctx, pe->metric_expr)) {
		/*
		* 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)) {
		expr_failure("Parse failed", map, pe);
		ret++;
		}
		}
		}
		}
		expr__ctx_free(ctx);
		/* TODO: fail when not ok */
		exit:
		@@ -1054,10 +1064,20 @@ static int metric_parse_fake(const char *str)
		}
		}

		if (expr__parse(&result, ctx, str))
		pr_err("expr__parse failed\n");
		else
		ret = 0;
		if (expr__parse(&result, ctx, str)) {
		/*
		* 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)) {
		pr_err("expr__parse failed\n");
		ret = -1;
		}
		}

		out:
		expr__ctx_free(ctx);