linux-kernel - [PATCH v2 3/3] perf-test: add a test for perf-stat --bpf-counters option

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Date:   Tue, 16 Mar 2021 14:18:37 -0700
From:   Song Liu <songliubraving@...com>
To:     <linux-kernel@...r.kernel.org>
CC:     <kernel-team@...com>, <acme@...nel.org>, <acme@...hat.com>,
        <namhyung@...nel.org>, <jolsa@...nel.org>,
        Song Liu <songliubraving@...com>
Subject: [PATCH v2 3/3] perf-test: add a test for perf-stat --bpf-counters option

Add a test to compare the output of perf-stat with and without option
--bpf-counters. If the difference is more than 10%, the test is considered
as failed.

For stable results between two runs (w/ and w/o --bpf-counters), the test
program should: 1) be long enough for better signal-noise-ratio; 2) not
depend on the behavior of IO subsystem (for less noise from caching). So
far, the best option we found is stressapptest.

Signed-off-by: Song Liu <songliubraving@...com>
---
 tools/perf/tests/shell/stat_bpf_counters.sh | 34 +++++++++++++++++++++
 1 file changed, 34 insertions(+)
 create mode 100755 tools/perf/tests/shell/stat_bpf_counters.sh

diff --git a/tools/perf/tests/shell/stat_bpf_counters.sh b/tools/perf/tests/shell/stat_bpf_counters.sh
new file mode 100755
index 0000000000000..c0bcb38d6b53c
--- /dev/null
+++ b/tools/perf/tests/shell/stat_bpf_counters.sh
@@ -0,0 +1,34 @@
+#!/bin/sh
+# perf stat --bpf-counters test
+# SPDX-License-Identifier: GPL-2.0
+
+set -e
+
+# check whether $2 is within +/- 10% of $1
+compare_number()
+{
+	first_num=$1
+	second_num=$2
+
+	# upper bound is first_num * 110%
+	upper=$(( $first_num + $first_num / 10 ))
+	# lower bound is first_num * 90%
+	lower=$(( $first_num - $first_num / 10 ))
+
+	if [ $second_num -gt $upper ] || [ $second_num -lt $lower ]; then
+		echo "The difference between $first_num and $second_num are greater than 10%."
+		exit 1
+	fi
+}
+
+# skip if --bpf-counters is not supported
+perf stat --bpf-counters true > /dev/null 2>&1 || exit 2
+
+# skip if stressapptest is not available
+stressapptest -s 1 -M 100 -m 1 > /dev/null 2>&1 || exit 2
+
+base_cycles=$(perf stat --no-big-num -e cycles -- stressapptest -s 3 -M 100 -m 1 2>&1 | grep -e cycles | awk '{print $1}')
+bpf_cycles=$(perf stat --no-big-num --bpf-counters -e cycles -- stressapptest -s 3 -M 100 -m 1 2>&1 | grep -e cycles | awk '{print $1}')
+
+compare_number $base_cycles $bpf_cycles
+exit 0
-- 
2.30.2