Re: [PATCH v3 10/10] selftests/resctrl: Reduce L2 impact on CAT test

Ilpo Järvinen
2026-03-27T17:49:58Z

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On Fri, 13 Mar 2026, Reinette Chatre wrote:

> The L3 CAT test loads a buffer into cache that is proportional to the L3
> size allocated for the workload and measures cache misses when accessing
> the buffer as a test of L3 occupancy. When loading the buffer it can be
> assumed that a portion of the buffer will be loaded into the L2 cache and
> depending on cache design may not be present in L3. It is thus possible
> for data to not be in L3 but also not trigger an L3 cache miss when
> accessed.
>
> Reduce impact of L2 on the L3 CAT test by, if L2 allocation is supported,
> minimizing the portion of L2 that the workload can allocate into. This
> encourages most of buffer to be loaded into L3 and support better
> comparison between buffer size, cache portion, and cache misses when
> accessing the buffer.
>
> Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
> Tested-by: Chen Yu <yu.c.chen@intel.com>
> ---
> Changes since v2:
> - Add Chen Yu's tag.
> ---
> tools/testing/selftests/resctrl/cat_test.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/tools/testing/selftests/resctrl/cat_test.c b/tools/testing/selftests/resctrl/cat_test.c
> index 6aac03147d41..371a2f26dc47 100644
> --- a/tools/testing/selftests/resctrl/cat_test.c
> +++ b/tools/testing/selftests/resctrl/cat_test.c
> @@ -157,6 +157,10 @@ static int cat_test(const struct resctrl_test *test,
> if (ret)
> goto reset_affinity;
>
> + ret = minimize_l2_occupancy(test, uparams, param);
> + if (ret)
> + goto reset_affinity;
> +
> perf_event_attr_initialize(&pea, PERF_COUNT_HW_CACHE_MISSES);
> pe_fd = perf_open(&pea, bm_pid, uparams->cpu);
> if (pe_fd < 0) {
>

Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

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