diff mbox series

[v3,09/29] selftests/resctrl: Create cache_portion_size() helper

Message ID 20231211121826.14392-10-ilpo.jarvinen@linux.intel.com
State Superseded
Headers show
Series selftests/resctrl: CAT test improvements & generalized test framework | expand

Commit Message

Ilpo Järvinen Dec. 11, 2023, 12:18 p.m. UTC 
CAT and CMT tests calculate size of the cache portion for the n-bits
cache allocation on their own.

Add cache_portion_size() helper that calculates size of the cache
portion for the given number of bits and use it to replace the existing
span calculations. This also prepares for the new CAT test that will
need to determine the size of the cache portion also during results
processing.

Rename also 'cache_size' local variables to 'cache_total_size' to
prevent misinterpretations.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
---
 tools/testing/selftests/resctrl/cat_test.c | 10 +++++-----
 tools/testing/selftests/resctrl/cmt_test.c |  8 ++++----
 tools/testing/selftests/resctrl/resctrl.h  | 15 +++++++++++++++
 3 files changed, 24 insertions(+), 9 deletions(-)

Comments

Reinette Chatre Dec. 13, 2023, 9:56 p.m. UTC | #1 
Hi Ilpo,

On 12/11/2023 4:18 AM, Ilpo Järvinen wrote:
> +/*
> + * cache_portion_size - Calculate the size of a cache portion
> + * @cache_size:		Total cache size in bytes
> + * @portion_mask:	Cache portion mask
> + * @full_cache_mask:	Full Cache Bit Mask (CBM) for the cache
> + *
> + * Return: The size of the cache portion in bytes.
> + */
> +static inline int cache_portion_size(unsigned long cache_size,
> +				     unsigned long portion_mask,
> +				     unsigned long full_cache_mask)
> +{
> +	return cache_size * count_bits(portion_mask) / count_bits(full_cache_mask);
> +}
> +

Even after you added the new zero check the static checker I tried
was not able to recognize that this is safe. Could you please add a check
to ensure that there will be no divide-by-zero here?

Reinette
Ilpo Järvinen Dec. 14, 2023, 10:16 a.m. UTC | #2 
On Wed, 13 Dec 2023, Reinette Chatre wrote:

> Hi Ilpo,
> 
> On 12/11/2023 4:18 AM, Ilpo Järvinen wrote:
> > +/*
> > + * cache_portion_size - Calculate the size of a cache portion
> > + * @cache_size:		Total cache size in bytes
> > + * @portion_mask:	Cache portion mask
> > + * @full_cache_mask:	Full Cache Bit Mask (CBM) for the cache
> > + *
> > + * Return: The size of the cache portion in bytes.
> > + */
> > +static inline int cache_portion_size(unsigned long cache_size,
> > +				     unsigned long portion_mask,
> > +				     unsigned long full_cache_mask)
> > +{
> > +	return cache_size * count_bits(portion_mask) / count_bits(full_cache_mask);
> > +}
> > +
> 
> Even after you added the new zero check the static checker I tried
> was not able to recognize that this is safe. Could you please add a check
> to ensure that there will be no divide-by-zero here?

Okay. I also now noticed the return type is not what it should be.
diff mbox series

Patch

diff --git a/tools/testing/selftests/resctrl/cat_test.c b/tools/testing/selftests/resctrl/cat_test.c
index 242c4c6200aa..f18c95dda5d3 100644
--- a/tools/testing/selftests/resctrl/cat_test.c
+++ b/tools/testing/selftests/resctrl/cat_test.c
@@ -91,7 +91,7 @@  int cat_perf_miss_val(int cpu_no, int n, char *cache_type)
 {
 	unsigned long l_mask, l_mask_1;
 	int ret, pipefd[2], sibling_cpu_no;
-	unsigned long cache_size = 0;
+	unsigned long cache_total_size = 0;
 	unsigned long long_mask;
 	int count_of_bits;
 	char pipe_message;
@@ -102,10 +102,10 @@  int cat_perf_miss_val(int cpu_no, int n, char *cache_type)
 		return ret;
 
 	/* Get L3/L2 cache size */
-	ret = get_cache_size(cpu_no, cache_type, &cache_size);
+	ret = get_cache_size(cpu_no, cache_type, &cache_total_size);
 	if (ret)
 		return ret;
-	ksft_print_msg("Cache size :%lu\n", cache_size);
+	ksft_print_msg("Cache size :%lu\n", cache_total_size);
 
 	count_of_bits = count_bits(long_mask);
 
@@ -136,7 +136,7 @@  int cat_perf_miss_val(int cpu_no, int n, char *cache_type)
 	/* Set param values for parent thread which will be allocated bitmask
 	 * with (max_bits - n) bits
 	 */
-	span = cache_size * (count_of_bits - n) / count_of_bits;
+	span = cache_portion_size(cache_total_size, l_mask, long_mask);
 	strcpy(param.ctrlgrp, "c2");
 	strcpy(param.mongrp, "m2");
 	strcpy(param.filename, RESULT_FILE_NAME2);
@@ -158,7 +158,7 @@  int cat_perf_miss_val(int cpu_no, int n, char *cache_type)
 		param.mask = l_mask_1;
 		strcpy(param.ctrlgrp, "c1");
 		strcpy(param.mongrp, "m1");
-		span = cache_size * n / count_of_bits;
+		span = cache_portion_size(cache_total_size, l_mask_1, long_mask);
 		strcpy(param.filename, RESULT_FILE_NAME1);
 		param.num_of_runs = 0;
 		param.cpu_no = sibling_cpu_no;
diff --git a/tools/testing/selftests/resctrl/cmt_test.c b/tools/testing/selftests/resctrl/cmt_test.c
index a18c6825802c..a14d46353865 100644
--- a/tools/testing/selftests/resctrl/cmt_test.c
+++ b/tools/testing/selftests/resctrl/cmt_test.c
@@ -72,7 +72,7 @@  int cmt_resctrl_val(int cpu_no, int n, const char * const *benchmark_cmd)
 {
 	const char * const *cmd = benchmark_cmd;
 	const char *new_cmd[BENCHMARK_ARGS];
-	unsigned long cache_size = 0;
+	unsigned long cache_total_size = 0;
 	unsigned long long_mask;
 	char *span_str = NULL;
 	int count_of_bits;
@@ -83,10 +83,10 @@  int cmt_resctrl_val(int cpu_no, int n, const char * const *benchmark_cmd)
 	if (ret)
 		return ret;
 
-	ret = get_cache_size(cpu_no, "L3", &cache_size);
+	ret = get_cache_size(cpu_no, "L3", &cache_total_size);
 	if (ret)
 		return ret;
-	ksft_print_msg("Cache size :%lu\n", cache_size);
+	ksft_print_msg("Cache size :%lu\n", cache_total_size);
 
 	count_of_bits = count_bits(long_mask);
 
@@ -107,7 +107,7 @@  int cmt_resctrl_val(int cpu_no, int n, const char * const *benchmark_cmd)
 		.setup		= cmt_setup,
 	};
 
-	span = cache_size * n / count_of_bits;
+	span = cache_portion_size(cache_total_size, param.mask, long_mask);
 
 	if (strcmp(cmd[0], "fill_buf") == 0) {
 		/* Duplicate the command to be able to replace span in it */
diff --git a/tools/testing/selftests/resctrl/resctrl.h b/tools/testing/selftests/resctrl/resctrl.h
index 9e5777e1eee3..0e3a4da5f6ec 100644
--- a/tools/testing/selftests/resctrl/resctrl.h
+++ b/tools/testing/selftests/resctrl/resctrl.h
@@ -116,4 +116,19 @@  int show_cache_info(unsigned long sum_llc_val, int no_of_bits,
 		    unsigned long max_diff_percent, unsigned long num_of_runs,
 		    bool platform, bool cmt);
 
+/*
+ * cache_portion_size - Calculate the size of a cache portion
+ * @cache_size:		Total cache size in bytes
+ * @portion_mask:	Cache portion mask
+ * @full_cache_mask:	Full Cache Bit Mask (CBM) for the cache
+ *
+ * Return: The size of the cache portion in bytes.
+ */
+static inline int cache_portion_size(unsigned long cache_size,
+				     unsigned long portion_mask,
+				     unsigned long full_cache_mask)
+{
+	return cache_size * count_bits(portion_mask) / count_bits(full_cache_mask);
+}
+
 #endif /* RESCTRL_H */