[PATCH v2 6/6] selftests/resctrl: Reduce failures due to outliers in MBA/MBM tests

Ilpo Järvinen
2023-09-15T15:46:16Z

The initial value of 5% chosen for the maximum allowed percentage
difference between resctrl mbm value and IMC mbm value in commit
06bd03a57f8c ("selftests/resctrl: Fix MBA/MBM results reporting
format") was "randomly chosen value" (as admitted by the changelog).

When running tests in our lab across a large number platforms, 5%
difference upper bound for success seems a bit on the low side for the
MBA and MBM tests. Some platforms produce outliers that are slightly
above that, typically 6-7%, which leads MBA/MBM test frequently
failing.

Replace the "randomly chosen value" with a success bound that is based
on those measurements across large number of platforms by relaxing the
MBA/MBM success bound to 8%. The relaxed bound removes the failures due
the frequent outliers.

Fixes: 06bd03a57f8c ("selftests/resctrl: Fix MBA/MBM results reporting format")
Cc: <stable@vger.kernel.org>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
---
tools/testing/selftests/resctrl/mba_test.c | 2 +-
tools/testing/selftests/resctrl/mbm_test.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/resctrl/mba_test.c b/tools/testing/selftests/resctrl/mba_test.c
index cf8284dadcb2..d3bf4368341e 100644
--- a/tools/testing/selftests/resctrl/mba_test.c
+++ b/tools/testing/selftests/resctrl/mba_test.c
@@ -12,7 +12,7 @@

#define RESULT_FILE_NAME "result_mba"
#define NUM_OF_RUNS 5
-#define MAX_DIFF_PERCENT 5
+#define MAX_DIFF_PERCENT 8
#define ALLOCATION_MAX 100
#define ALLOCATION_MIN 10
#define ALLOCATION_STEP 10
diff --git a/tools/testing/selftests/resctrl/mbm_test.c b/tools/testing/selftests/resctrl/mbm_test.c
index 1ae131a2e246..d3c0d30c676a 100644
--- a/tools/testing/selftests/resctrl/mbm_test.c
+++ b/tools/testing/selftests/resctrl/mbm_test.c
@@ -11,7 +11,7 @@
#include "resctrl.h"

#define RESULT_FILE_NAME "result_mbm"
-#define MAX_DIFF_PERCENT 5
+#define MAX_DIFF_PERCENT 8
#define NUM_OF_RUNS 5

static int
--
2.30.2