Re: [PATCH v5 2/2] perf pmu intel: Adjust cpumaks for sub-NUMA clusters on Emeraldrapids

Namhyung Kim
2026-04-10T04:43:19Z

On Tue, Apr 07, 2026 at 01:38:43PM -0700, Chun-Tse Shao wrote:
> Similar to GNR [1], Emeraldrapids supports sub-NUMA clusters as well.
> Adjust cpumasks as the logic for GNR in [1].
>
> Tested on Emeraldrapids with SNC2 enabled:
> $ perf stat --per-node -e 'UNC_CHA_CLOCKTICKS,UNC_M_CLOCKTICKS' -a -- sleep 1
>
> Performance counter stats for 'system wide':
>
> N0 30 72125876670 UNC_CHA_CLOCKTICKS
> N0 4 8815163648 UNC_M_CLOCKTICKS
> N1 30 72124958844 UNC_CHA_CLOCKTICKS
> N1 4 8815014974 UNC_M_CLOCKTICKS
> N2 30 72121049022 UNC_CHA_CLOCKTICKS
> N2 4 8814592626 UNC_M_CLOCKTICKS
> N3 30 72117133854 UNC_CHA_CLOCKTICKS
> N3 4 8814012840 UNC_M_CLOCKTICKS
>
> 1.001574118 seconds time elapsed
>
> [1] lore.kernel.org/20250515181417.491401-1-irogers@google.com
>
> Reviewed-by: Zide Chen <zide.chen@intel.com>
> Reviewed-by: Ian Rogers <irogers@google.com>
> Signed-off-by: Chun-Tse Shao <ctshao@google.com>
> ---
> tools/perf/arch/x86/util/pmu.c | 56 +++++++++++++++++++++++-----------
> 1 file changed, 38 insertions(+), 18 deletions(-)
>
> diff --git a/tools/perf/arch/x86/util/pmu.c b/tools/perf/arch/x86/util/pmu.c
> index 938be36ec0f7..3743f5145505 100644
> --- a/tools/perf/arch/x86/util/pmu.c
> +++ b/tools/perf/arch/x86/util/pmu.c
> @@ -30,8 +30,9 @@ static bool x86__is_snc_supported(void)
>
> if (!checked_if_snc_supported) {
>
> - /* Graniterapids supports SNC configuration. */
> + /* Emeraldrapids Graniterapids support SNC configuration. */
> static const char *const supported_cpuids[] = {
> + "GenuineIntel-6-CF", /* Emeraldrapids */
> "GenuineIntel-6-A[DE]", /* Graniterapids */

It'd be great if we can share these string literals..

> };
> char *cpuid = get_cpuid_str((struct perf_cpu){0});
> @@ -141,23 +142,42 @@ static int uncore_imc_snc(struct perf_pmu *pmu)
> // Compute the IMC SNC using lookup tables.
> unsigned int imc_num;
> int snc_nodes = snc_nodes_per_l3_cache();
> - const u8 snc2_map[] = {1, 1, 0, 0};
> - const u8 snc3_map[] = {1, 1, 0, 0, 2, 2};
> - const u8 *snc_map;
> - size_t snc_map_len;
> -
> - switch (snc_nodes) {
> - case 2:
> - snc_map = snc2_map;
> - snc_map_len = ARRAY_SIZE(snc2_map);
> - break;
> - case 3:
> - snc_map = snc3_map;
> - snc_map_len = ARRAY_SIZE(snc3_map);
> - break;
> - default:
> - /* Error or no lookup support for SNC with >3 nodes. */
> - return 0;
> + char *cpuid;
> + static const u8 emr_snc2_map[] = { 0, 0, 1, 1 };
> + static const u8 gnr_snc2_map[] = { 1, 1, 0, 0 };
> + static const u8 snc3_map[] = { 1, 1, 0, 0, 2, 2 };
> + static const u8 *snc_map;
> + static size_t snc_map_len;
> +
> + /* snc_map is not inited yet. We only look up once to avoid expensive operations. */
> + if (!snc_map) {
> + switch (snc_nodes) {
> + case 2:
> + cpuid = get_cpuid_str((struct perf_cpu){ 0 });
> + if (cpuid) {
> + if (strcmp_cpuid_str("GenuineIntel-6-CF", cpuid) == 0) {
> + snc_map = emr_snc2_map;
> + snc_map_len = ARRAY_SIZE(emr_snc2_map);
> + } else if (strcmp_cpuid_str("GenuineIntel-6-A[DE]", cpuid) == 0) {
> + snc_map = gnr_snc2_map;
> + snc_map_len = ARRAY_SIZE(gnr_snc2_map);

... in here as well.

Thanks,
Namhyung

> + }
> + free(cpuid);
> + }
> + break;
> + case 3:
> + snc_map = snc3_map;
> + snc_map_len = ARRAY_SIZE(snc3_map);
> + break;
> + default:
> + /* Error or no lookup support for SNC with >3 nodes. */
> + return 0;
> + }
> +
> + if (!snc_map) {
> + pr_warning("Unexpected: can not find snc map config");
> + return 0;
> + }
> }
>
> /* Compute SNC for PMU. */
> --
> 2.53.0.1213.gd9a14994de-goog
>