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Message-ID: <CAP-5=fVLFVzitYZso2HB7dFgaNbJqW0pLE_AqMhc0ytW0PFvZw@mail.gmail.com>
Date: Thu, 8 Jan 2026 11:19:16 -0800
From: Ian Rogers <irogers@...gle.com>
To: Chun-Tse Shao <ctshao@...gle.com>, Thomas Falcon <thomas.falcon@...el.com>,
Dapeng Mi <dapeng1.mi@...ux.intel.com>
Cc: linux-kernel@...r.kernel.org, peterz@...radead.org, mingo@...hat.com,
acme@...nel.org, namhyung@...nel.org, mark.rutland@....com,
alexander.shishkin@...ux.intel.com, jolsa@...nel.org, adrian.hunter@...el.com,
james.clark@...aro.org, ravi.bangoria@....com,
linux-perf-users@...r.kernel.org
Subject: Re: [PATCH] perf pmu intel: Adjust cpumaks for sub-NUMA clusters on Emeraldrapids
On Thu, Jan 8, 2026 at 10:45 AM Chun-Tse Shao <ctshao@...gle.com> 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>
> ---
> tools/perf/arch/x86/util/pmu.c | 45 +++++++++++++++++++++-------------
> 1 file changed, 28 insertions(+), 17 deletions(-)
>
> diff --git a/tools/perf/arch/x86/util/pmu.c b/tools/perf/arch/x86/util/pmu.c
> index a3f96221758d..fad68a0f7b5d 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;
> }
>
> 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;
> @@ -137,8 +147,8 @@ 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 snc2_map[] = {0, 0, 1, 1};
Does this alter the behavior on GNR? ie 1,1,0,0 vs 0,0,1,1.
Thanks,
Ian
> + const u8 snc3_map[] = {1, 1, 0, 0, 2, 2};
> const u8 *snc_map;
> size_t snc_map_len;
>
> @@ -161,11 +171,11 @@ 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 +215,7 @@ 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 +314,12 @@ 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);
> }
> }
> }
> --
> 2.52.0.457.g6b5491de43-goog
>
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