Hi Ilpo,
On 10/24/2023 2:26 AM, Ilpo Järvinen wrote:
> CAT test doesn't take shareable bits into account, i.e., the test might
> be sharing cache with some devices (e.g., graphics).
>
> Introduce get_mask_no_shareable() and use it to provision an
> environment for CAT test where the allocated LLC is isolated better.
> Excluding shareable_bits may create hole(s) into the cbm_mask, thus add
> a new helper count_contiguous_bits() to find the longest contiguous set
> of CBM bits.
>
> create_bit_mask() is needed by an upcoming CAT test rewrite so make it
> available in resctrl.h right away.
>
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
> ---
> tools/testing/selftests/resctrl/cat_test.c | 12 ++-
> tools/testing/selftests/resctrl/resctrl.h | 3 +
> tools/testing/selftests/resctrl/resctrlfs.c | 84 +++++++++++++++++++++
> 3 files changed, 95 insertions(+), 4 deletions(-)
>
> diff --git a/tools/testing/selftests/resctrl/cat_test.c b/tools/testing/selftests/resctrl/cat_test.c
> index 80861c362a53..e5861e7cba7e 100644
> --- a/tools/testing/selftests/resctrl/cat_test.c
> +++ b/tools/testing/selftests/resctrl/cat_test.c
> @@ -92,13 +92,17 @@ 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_total_size = 0;
> - unsigned long long_mask;
> + unsigned long full_cache_mask, long_mask;
Please do maintain reverse fir order.
> int count_of_bits;
> char pipe_message;
> size_t span;
>
> /* Get default cbm mask for L3/L2 cache */
> - ret = get_cbm_mask(cache_type, &long_mask);
> + ret = get_cbm_mask(cache_type, &full_cache_mask);
> + if (ret)
> + return ret;
> + /* Get the exclusive portion of the cache */
> + ret = get_mask_no_shareable(cache_type, &long_mask);
> if (ret)
> return ret;
>
> +
> +/*
> + * count_contiguous_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 contiguous bits in the longest train of bits
> + */
> +static unsigned int count_contiguous_bits(unsigned long val, unsigned int *start)
> +{
> + unsigned long last_val;
> + int count = 0;
could count be unsigned int?
> +
> + 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_mask - Get cbm bit mask
> * @cache_type: Cache level L2/L3
> @@ -253,6 +291,52 @@ int get_cbm_mask(const char *cache_type, unsigned long *mask)
> return 0;
> }
>
> +/*
> + * get_shareable_mask - Get shareable mask from shareable_bits for given cache
> + * @cache_type: Cache level L2/L3
> + * @shareable_mask: shareable mask returned as unsigned long
A nitpick but please be consistent in starting sentences with capital letter.
> + *
> + * Return: = 0 on success, < 0 on failure.
> + */
> +int get_shareable_mask(const char *cache_type, unsigned long *shareable_mask)
> +{
> + char mask_path[1024];
> +
> + if (!cache_type)
> + return -1;
Same question as earlier about error checking.
> +
> + snprintf(mask_path, sizeof(mask_path), "%s/%s/shareable_bits",
> + INFO_PATH, cache_type);
> +
> + return get_bit_mask(mask_path, shareable_mask);
> +}
> +
> +/*
> + * get_mask_no_shareable - Get CBM mask without shareable_bits for given cache
> + * @cache_type: Cache level L2/L3
> + * @mask: mask returned as unsigned long
Apart from comment about capital letter this comment does not seem to
reveal more about what code does.
> + *
> + * Return: = 0 on success, < 0 on failure.
> + */
> +int get_mask_no_shareable(const char *cache_type, unsigned long *mask)
> +{
> + unsigned long full_mask, shareable_mask;
> + unsigned int start, len;
> +
> + if (get_cbm_mask(cache_type, &full_mask) < 0)
> + return -1;
> + if (get_shareable_mask(cache_type, &shareable_mask) < 0)
> + return -1;
> +
> + len = count_contiguous_bits(full_mask & ~shareable_mask, &start);
> + if (!len)
> + return -1;
> +
> + *mask = create_bit_mask(start, len);
> +
> + return 0;
> +}
Nicely done, thanks.
> +
> /*
> * get_core_sibling - Get sibling core id from the same socket for given CPU
> * @cpu_no: CPU number
Reinette
