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Message-ID: <CAJpZYjVadSgX6eSczFsqxJpMSq8q67CkA_WA+8jf+atgUScBNA@mail.gmail.com>
Date: Tue, 13 Jan 2026 10:06:54 -0800
From: Chun-Tse Shao <ctshao@...gle.com>
To: Ian Rogers <irogers@...gle.com>
Cc: Thomas Falcon <thomas.falcon@...el.com>, Dapeng Mi <dapeng1.mi@...ux.intel.com>,
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
Ping.
Thanks for your comment, Ian. To Intel team, can we get confirmation
of the GNR SNR2 configuration?
-CT
On Thu, Jan 8, 2026 at 11:19 AM Ian Rogers <irogers@...gle.com> wrote:
>
> 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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