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Message-ID: <ad625513-70a8-444d-a389-226715d2a86d@intel.com>
Date: Fri, 6 Feb 2026 15:46:36 -0800
From: "Chen, Zide" <zide.chen@...el.com>
To: Chun-Tse Shao <ctshao@...gle.com>, linux-kernel@...r.kernel.org
Cc: peterz@...radead.org, mingo@...hat.com, acme@...nel.org,
namhyung@...nel.org, mark.rutland@....com,
alexander.shishkin@...ux.intel.com, jolsa@...nel.org, irogers@...gle.com,
adrian.hunter@...el.com, james.clark@...aro.org, ravi.bangoria@....com,
linux-perf-users@...r.kernel.org
Subject: Re: [PATCH v2] perf pmu intel: Adjust cpumaks for sub-NUMA clusters
on Emeraldrapids
On 2/5/2026 3:21 PM, 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@...gle.com
>
> Signed-off-by: Chun-Tse Shao <ctshao@...gle.com>
> ---
> v2:
> Split EMR and GNR in the SNC2 IMC cpu map.
>
> v1: lore.kernel.org/20260108184430.1210223-1-ctshao@...gle.com
>
> tools/perf/arch/x86/util/pmu.c | 95 ++++++++++++++++++++++------------
> 1 file changed, 63 insertions(+), 32 deletions(-)
>
> diff --git a/tools/perf/arch/x86/util/pmu.c b/tools/perf/arch/x86/util/pmu.c
> index a3f96221758d..dbe876cd1b08 100644
> --- a/tools/perf/arch/x86/util/pmu.c
> +++ b/tools/perf/arch/x86/util/pmu.c
> @@ -22,20 +22,29 @@
> #include "util/env.h"
> #include "util/header.h"
>
> -static bool x86__is_intel_graniterapids(void)
> +static bool x86__is_snc_supported(void)
> {
> - static bool checked_if_graniterapids;
> - static bool is_graniterapids;
> + static bool checked_if_snc_supported;
> + static bool is_supported;
>
> - if (!checked_if_graniterapids) {
> - const char *graniterapids_cpuid = "GenuineIntel-6-A[DE]";
> + if (!checked_if_snc_supported) {
> +
> + /* Emeraldrapids and Graniterapids support SNC configuration. */
> + static const char *const supported_cpuids[] = {
> + "GenuineIntel-6-CF", /* Emeraldrapids */
> + "GenuineIntel-6-A[DE]", /* Graniterapids */
> + };
> char *cpuid = get_cpuid_str((struct perf_cpu){0});
>
> - is_graniterapids = cpuid && strcmp_cpuid_str(graniterapids_cpuid, cpuid) == 0;
> + for (size_t i = 0; i < ARRAY_SIZE(supported_cpuids); i++) {
> + is_supported = cpuid && strcmp_cpuid_str(supported_cpuids[i], cpuid) == 0;
> + if (is_supported)
> + break;
> + }
> free(cpuid);
> - checked_if_graniterapids = true;
> + checked_if_snc_supported = true;
> }
> - return is_graniterapids;
> + return checked_if_snc_supported;
This appears to be a typo, supposed to be is_supported.
> }
>
> static struct perf_cpu_map *read_sysfs_cpu_map(const char *sysfs_path)
> @@ -64,6 +73,7 @@ static int snc_nodes_per_l3_cache(void)
> read_sysfs_cpu_map("devices/system/cpu/cpu0/cache/index3/shared_cpu_list");
>
> snc_nodes = perf_cpu_map__nr(cache_cpus) / perf_cpu_map__nr(node_cpus);
> +
> perf_cpu_map__put(cache_cpus);
> perf_cpu_map__put(node_cpus);
> checked_snc = true;
> @@ -137,23 +147,42 @@ 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, 1, 1, 0, 0};
> - const u8 snc3_map[] = {1, 1, 0, 0, 2, 2, 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 = NULL;
> + 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);
> + }
> + 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. */
> @@ -161,11 +190,12 @@ static int uncore_imc_snc(struct perf_pmu *pmu)
> pr_warning("Unexpected: unable to compute IMC number '%s'\n", pmu->name);
> return 0;
> }
> - if (imc_num >= snc_map_len) {
> + if (imc_num >= snc_map_len * perf_cpu_map__nr(pmu->cpus)) {
> pr_warning("Unexpected IMC %d for SNC%d mapping\n", imc_num, snc_nodes);
> return 0;
> }
> - return snc_map[imc_num];
> +
> + return snc_map[imc_num % snc_map_len];
> }
>
> static int uncore_cha_imc_compute_cpu_adjust(int pmu_snc)
> @@ -205,7 +235,7 @@ static int uncore_cha_imc_compute_cpu_adjust(int pmu_snc)
> return cpu_adjust[pmu_snc];
> }
>
> -static void gnr_uncore_cha_imc_adjust_cpumask_for_snc(struct perf_pmu *pmu, bool cha)
> +static void uncore_cha_imc_adjust_cpumask_for_snc(struct perf_pmu *pmu, bool cha)
> {
> // With sub-NUMA clustering (SNC) there is a NUMA node per SNC in the
> // topology. For example, a two socket graniterapids machine may be set
> @@ -304,11 +334,12 @@ void perf_pmu__arch_init(struct perf_pmu *pmu)
> pmu->mem_events = perf_mem_events_intel_aux;
> else
> pmu->mem_events = perf_mem_events_intel;
> - } else if (x86__is_intel_graniterapids()) {
> + } else if (x86__is_snc_supported()) {
> if (starts_with(pmu->name, "uncore_cha_"))
> - gnr_uncore_cha_imc_adjust_cpumask_for_snc(pmu, /*cha=*/true);
> - else if (starts_with(pmu->name, "uncore_imc_"))
> - gnr_uncore_cha_imc_adjust_cpumask_for_snc(pmu, /*cha=*/false);
> + uncore_cha_imc_adjust_cpumask_for_snc(pmu, /*cha=*/true);
> + else if (starts_with(pmu->name, "uncore_imc_") &&
> + !starts_with(pmu->name, "uncore_imc_free_running"))
> + uncore_cha_imc_adjust_cpumask_for_snc(pmu, /*cha=*/false);
> }
> }
> }
> --
> 2.53.0.rc2.204.g2597b5adb4-goog
>
>
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