selftests/resctrl: Keep results from first test run

JIRA: https://issues.redhat.com/browse/RHEL-118965

commit 295b898
Author: Reinette Chatre <reinette.chatre@intel.com>
Date:   Thu Oct 24 14:18:51 2024 -0700

    selftests/resctrl: Keep results from first test run

    The resctrl selftests drop the results from every first test run
    to avoid (per comment) "inaccurate due to monitoring setup transition
    phase" data. Previously inaccurate data resulted from workloads needing
    some time to "settle" and also the measurements themselves to
    account for earlier measurements to measure across needed timeframe.

    commit da50de0 ("selftests/resctrl: Calculate resctrl FS derived mem
    bw over sleep(1) only")

    ensured that measurements accurately measure just the time frame of
    interest. The default "fill_buf" benchmark since separated the buffer
    prepare phase from the benchmark run phase reducing the need for the
    tests themselves to accommodate the benchmark's "settle" time.

    With these enhancements there are no remaining portions needing
    to "settle" and the first test run can contribute to measurements.

    Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
    Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
    Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

Signed-off-by: David Arcari <darcari@redhat.com>

Author: darcari

tools/testing/selftests/resctrl/cmt_test.c

@@ -99,14 +99,13 @@ static int check_results(struct resctrl_val_param *param, size_t span, int no_of
 		}
 
 		/* Field 3 is llc occ resc value */
-		if (runs > 0)
-			sum_llc_occu_resc += strtoul(token_array[3], NULL, 0);
+		sum_llc_occu_resc += strtoul(token_array[3], NULL, 0);
 		runs++;
 	}
 	fclose(fp);
 
 	return show_results_info(sum_llc_occu_resc, no_of_bits, span,
-				 MAX_DIFF, MAX_DIFF_PERCENT, runs - 1, true);
+				 MAX_DIFF, MAX_DIFF_PERCENT, runs, true);
 }
 
 static void cmt_test_cleanup(void)

tools/testing/selftests/resctrl/mba_test.c

@@ -86,18 +86,14 @@ static bool show_mba_info(unsigned long *bw_imc, unsigned long *bw_resc)
 		int avg_diff_per;
 		float avg_diff;
 
-		/*
-		 * The first run is discarded due to inaccurate value from
-		 * phase transition.
-		 */
-		for (runs = NUM_OF_RUNS * allocation + 1;
+		for (runs = NUM_OF_RUNS * allocation;
 		     runs < NUM_OF_RUNS * allocation + NUM_OF_RUNS ; runs++) {
 			sum_bw_imc += bw_imc[runs];
 			sum_bw_resc += bw_resc[runs];
 		}
 
-		avg_bw_imc = sum_bw_imc / (NUM_OF_RUNS - 1);
-		avg_bw_resc = sum_bw_resc / (NUM_OF_RUNS - 1);
+		avg_bw_imc = sum_bw_imc / NUM_OF_RUNS;
+		avg_bw_resc = sum_bw_resc / NUM_OF_RUNS;
 		if (avg_bw_imc < THROTTLE_THRESHOLD || avg_bw_resc < THROTTLE_THRESHOLD) {
 			ksft_print_msg("Bandwidth below threshold (%d MiB). Dropping results from MBA schemata %u.\n",
 				       THROTTLE_THRESHOLD,

tools/testing/selftests/resctrl/mbm_test.c

@@ -22,17 +22,13 @@ show_bw_info(unsigned long *bw_imc, unsigned long *bw_resc, size_t span)
 	int runs, ret, avg_diff_per;
 	float avg_diff = 0;
 
-	/*
-	 * Discard the first value which is inaccurate due to monitoring setup
-	 * transition phase.
-	 */
-	for (runs = 1; runs < NUM_OF_RUNS ; runs++) {
+	for (runs = 0; runs < NUM_OF_RUNS; runs++) {
 		sum_bw_imc += bw_imc[runs];
 		sum_bw_resc += bw_resc[runs];
 	}
 
-	avg_bw_imc = sum_bw_imc / 4;
-	avg_bw_resc = sum_bw_resc / 4;
+	avg_bw_imc = sum_bw_imc / NUM_OF_RUNS;
+	avg_bw_resc = sum_bw_resc / NUM_OF_RUNS;
 	avg_diff = (float)labs(avg_bw_resc - avg_bw_imc) / avg_bw_imc;
 	avg_diff_per = (int)(avg_diff * 100);