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Message-ID: <CAJpZYjVDUQ=662uAnL71Pp4CmsUz+9toWmoMpNBjjcZOJUNv_w@mail.gmail.com>
Date: Fri, 23 Jan 2026 10:29:17 -0800
From: Chun-Tse Shao <ctshao@...gle.com>
To: "Chen, Zide" <zide.chen@...el.com>
Cc: "Mi, Dapeng" <dapeng1.mi@...ux.intel.com>, Ian Rogers <irogers@...gle.com>,
Thomas Falcon <thomas.falcon@...el.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
Thank you for the confirmation, Zide. I will submit another patch to
split EMR and GNR SNC2 IMC map.
-CT
On Thu, Jan 22, 2026 at 2:06 PM Chen, Zide <zide.chen@...el.com> wrote:
>
>
>
> On 1/18/2026 4:51 PM, Mi, Dapeng wrote:
> >
> > On 1/14/2026 2:06 AM, Chun-Tse Shao wrote:
> >> 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.
>
> It appears to break GNR SNC2. While it works for the --per-node test, it
> fails the following affinity test. Testing on EMR shows that it follows
> the new lookup table. Should we use a model-specific lookup table here?
>
> # Running workload on CPU0
> $ taskset -c CPU0 stress-ng --vm 1 --vm-bytes 2G --vm-method all
> --timeout 30s
>
> # Profiling UNC_M_PRE_COUNT.ALL on all IMC boxes.
> $ perf stat \
> -e uncore_imc_0/event=0x03,umask=0xFF/ \
> -e uncore_imc_1/event=0x03,umask=0xFF/ \
> -e uncore_imc_2/event=0x03,umask=0xFF/ \
> -e uncore_imc_3/event=0x03,umask=0xFF/ \
> -e uncore_imc_4/event=0x03,umask=0xFF/ \
> -e uncore_imc_5/event=0x03,umask=0xFF/ \
> -e uncore_imc_6/event=0x03,umask=0xFF/ \
> -e uncore_imc_7/event=0x03,umask=0xFF/ \
> -a -I 1000
>
> This shows that the uncore_imc_[2|3|6|7] boxes are affinitized to CPU0.
>
> 5.013638757 1,635,470 uncore_imc_0/event=0x03,umask=0xFF/
> 5.013638757 1,638,157 uncore_imc_1/event=0x03,umask=0xFF/
> 5.013638757 27,093,922 uncore_imc_2/event=0x03,umask=0xFF/
> 5.013638757 27,025,980 uncore_imc_3/event=0x03,umask=0xFF/
> 5.013638757 1,616,974 uncore_imc_4/event=0x03,umask=0xFF/
> 5.013638757 1,627,251 uncore_imc_5/event=0x03,umask=0xFF/
> 5.013638757 26,854,588 uncore_imc_6/event=0x03,umask=0xFF/
> 5.013638757 26,974,506 uncore_imc_7/event=0x03,umask=0xFF/
>
> Testing with additional CPUs confirms that the original GNR SNC2 lookup
> table is correct.
>
> CPU uncore_imc box
> NUMA node0 CPU(s): 0-42,344-386 2 3 6 7
> NUMA node1 CPU(s): 43-85,387-429 0 1 4 5
> NUMA node2 CPU(s): 86-128,430-472 2 3 6 7
> NUMA node3 CPU(s): 129-171,473-515 0 1 4 5
> NUMA node4 CPU(s): 172-214,516-558 2 3 6 7
> NUMA node5 CPU(s): 215-257,559-601 0 1 4 5
> NUMA node6 CPU(s): 258-300,602-644 2 3 6 7
> NUMA node7 CPU(s): 301-343,645-687 0 1 4 5
>
>
> >>> 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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