[PATCH v2 17/24] selftests/resctrl: Replace count_bits with count_consecutive_bits()

[Ilpo Järvinen]

CAT and CMT tests depends on masks being continuous.

Replace count_bits with more appropriate variant that counts
consecutive bits.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
---
 tools/testing/selftests/resctrl/cat_test.c  |  6 ++---
 tools/testing/selftests/resctrl/cmt_test.c  |  3 +--
 tools/testing/selftests/resctrl/resctrl.h   |  1 +
 tools/testing/selftests/resctrl/resctrlfs.c | 30 +++++++++++++++++++++
 4 files changed, 34 insertions(+), 6 deletions(-)

diff --git a/tools/testing/selftests/resctrl/cat_test.c b/tools/testing/selftests/resctrl/cat_test.c
index d3fbd4de9f8a..a1834dd5ad9a 100644
--- a/tools/testing/selftests/resctrl/cat_test.c
+++ b/tools/testing/selftests/resctrl/cat_test.c
@@ -78,7 +78,7 @@ static int check_results(struct resctrl_val_param *param)
 	}
 
 	fclose(fp);
-	no_of_bits = count_bits(param->mask);
+	no_of_bits = count_consecutive_bits(param->mask, NULL);
 
 	return show_cache_info(sum_llc_perf_miss, no_of_bits, param->span / 64,
 			       MAX_DIFF, MAX_DIFF_PERCENT, NUM_OF_RUNS,
@@ -103,6 +103,7 @@ int cat_perf_miss_val(int cpu_no, int n, char *cache_type)
 	ret = get_cbm_mask(cache_type, &long_mask);
 	if (ret)
 		return ret;
+	count_of_bits = count_consecutive_bits(long_mask, NULL);
 
 	/* Get L3/L2 cache size */
 	ret = get_cache_size(cpu_no, cache_type, &cache_size);
@@ -110,9 +111,6 @@ int cat_perf_miss_val(int cpu_no, int n, char *cache_type)
 		return ret;
 	ksft_print_msg("Cache size :%lu\n", cache_size);
 
-	/* Get max number of bits from default-cabm mask */
-	count_of_bits = count_bits(long_mask);
-
 	if (!n)
 		n = count_of_bits / 2;
 
diff --git a/tools/testing/selftests/resctrl/cmt_test.c b/tools/testing/selftests/resctrl/cmt_test.c
index efe77e0f1d4c..98e7d3accd73 100644
--- a/tools/testing/selftests/resctrl/cmt_test.c
+++ b/tools/testing/selftests/resctrl/cmt_test.c
@@ -84,14 +84,13 @@ int cmt_resctrl_val(int cpu_no, int n, char **benchmark_cmd)
 	ret = get_cbm_mask("L3", &long_mask);
 	if (ret)
 		return ret;
+	count_of_bits = count_consecutive_bits(long_mask, NULL);
 
 	ret = get_cache_size(cpu_no, "L3", &cache_size);
 	if (ret)
 		return ret;
 	ksft_print_msg("Cache size :%lu\n", cache_size);
 
-	count_of_bits = count_bits(long_mask);
-
 	if (n < 1 || n > count_of_bits) {
 		ksft_print_msg("Invalid input value for numbr_of_bits n!\n");
 		ksft_print_msg("Please enter value in range 1 to %d\n", count_of_bits);
diff --git a/tools/testing/selftests/resctrl/resctrl.h b/tools/testing/selftests/resctrl/resctrl.h
index 65425d92684e..aa5dc8b95a06 100644
--- a/tools/testing/selftests/resctrl/resctrl.h
+++ b/tools/testing/selftests/resctrl/resctrl.h
@@ -106,6 +106,7 @@ void tests_cleanup(void);
 void mbm_test_cleanup(void);
 int mba_schemata_change(int cpu_no, char *bw_report, char **benchmark_cmd);
 void mba_test_cleanup(void);
+unsigned int count_consecutive_bits(unsigned long val, unsigned int *start);
 int get_cbm_mask(char *cache_type, unsigned long *mask);
 int get_cache_size(int cpu_no, char *cache_type, unsigned long *cache_size);
 int cache_alloc_size(int cpu_no, char *cache_type, unsigned long alloc_mask,
diff --git a/tools/testing/selftests/resctrl/resctrlfs.c b/tools/testing/selftests/resctrl/resctrlfs.c
index f01ecfa64063..4efaf69c8152 100644
--- a/tools/testing/selftests/resctrl/resctrlfs.c
+++ b/tools/testing/selftests/resctrl/resctrlfs.c
@@ -10,6 +10,8 @@
  */
 #include "resctrl.h"
 
+#include <strings.h>
+
 static int find_resctrl_mount(char *buffer)
 {
 	FILE *mounts;
@@ -218,6 +220,34 @@ static int get_bit_mask(char *filename, unsigned long *mask)
 	return 0;
 }
 
+/*
+ * count_consecutive_bits - Returns the longest train of bits in a bit mask
+ * @val		A bit mask
+ * @start	The location of the least-significant bit of the longest train
+ *
+ * Return:	The length of the consecutive bits in the longest train of bits
+ */
+unsigned int count_consecutive_bits(unsigned long val, unsigned int *start)
+{
+	unsigned long last_val;
+	int count = 0;
+
+	while (val) {
+		last_val = val;
+		val &= (val >> 1);
+		count++;
+	}
+
+	if (start) {
+		if (count)
+			*start = ffsl(last_val) - 1;
+		else
+			*start = 0;
+	}
+
+	return count;
+}
+
 /*
  * get_cbm_bits - Get number of bits in cbm mask
  * @cache_type:		Cache level L2/L3
-- 
2.30.2