linux-kernel - [PATCH V4 15/15] selftests/resctrl: Replace magic constants used as array size

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Message-ID: <a1f4676c2db14841c3ffd9e575a41dc2bb8e77d7.1729804024.git.reinette.chatre@intel.com>
Date: Thu, 24 Oct 2024 14:18:52 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: fenghua.yu@...el.com,
	shuah@...nel.org,
	tony.luck@...el.com,
	peternewman@...gle.com,
	babu.moger@....com,
	ilpo.jarvinen@...ux.intel.com
Cc: maciej.wieczor-retman@...el.com,
	reinette.chatre@...el.com,
	linux-kselftest@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH V4 15/15] selftests/resctrl: Replace magic constants used as array size

The Memory Bandwidth Allocation (MBA) test iterates through all possible
MBA allocations, from 10% (ALLOCATION_MIN) to 100% (ALLOCATION_MAX) with
increments of 10% (ALLOCATION_STEP) at each iteration. During each
iteration the test measures the actual memory bandwidth NUM_OF_RUNS times
to determine the impact of MBA on actual memory bandwidth.

After the MBA test completes all the memory bandwidth measurements are
parsed into an array. One array for resctrl Memory Bandwidth Monitoring
(MBM) measurements and one array for the Integrated Memory Controller
(iMC) measurements. Each array has a hardcoded size of 1024 that is
large enough to hold the current test data, but this hardcoded value makes
the implementation difficult to understand. It will not be clear that this
array needs to be reconsidered if any of the test parameters are changed.

Replace the magic constant as array size with the test parameters the
array size depends on.

Reported-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Closes: https://lore.kernel.org/all/45af2a8c-517d-8f0d-137d-ad0f3f6a3c68@linux.intel.com/
Signed-off-by: Reinette Chatre <reinette.chatre@...el.com>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
---
Changes since V3:
- Add Ilpo's Reviewed-by tag.

Changes since V2:
- New patch.
---
 tools/testing/selftests/resctrl/mba_test.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/resctrl/mba_test.c b/tools/testing/selftests/resctrl/mba_test.c
index 4e6645b172e3..536d9089d2f6 100644
--- a/tools/testing/selftests/resctrl/mba_test.c
+++ b/tools/testing/selftests/resctrl/mba_test.c
@@ -127,8 +127,9 @@ static bool show_mba_info(unsigned long *bw_imc, unsigned long *bw_resc)

 static int check_results(void)
 {
+	unsigned long bw_resc[NUM_OF_RUNS * ALLOCATION_MAX / ALLOCATION_STEP];
+	unsigned long bw_imc[NUM_OF_RUNS * ALLOCATION_MAX / ALLOCATION_STEP];
 	char *token_array[8], output[] = RESULT_FILE_NAME, temp[512];
-	unsigned long bw_imc[1024], bw_resc[1024];
 	int runs;
 	FILE *fp;

-- 
2.47.0