| Message ID | 1799046.VLH7GnMWUR@kreacher |
|---|---|
| State | New |
| Headers | show |
| Series | x86 / intel_pstate: Set asymmetric CPU capacity on hybrid systems | expand |
On 25/04/2024 21:06, Rafael J. Wysocki wrote: > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > Make intel_pstate use the HWP_HIGHEST_PERF values from > MSR_HWP_CAPABILITIES to set asymmetric CPU capacity information > via the previously introduced arch_set_cpu_capacity() on hybrid > systems without SMT. Are there such systems around? My i7-13700K has P-cores (CPU0..CPU15) with SMT. > Setting asymmetric CPU capacity is generally necessary to allow the > scheduler to compute task sizes in a consistent way across all CPUs > in a system where they differ by capacity. That, in turn, should help > to improve task placement and load balancing decisions. It is also > necessary for the schedutil cpufreq governor to operate as expected > on hybrid systems where tasks migrate between CPUs of different > capacities. > > The underlying observation is that intel_pstate already uses > MSR_HWP_CAPABILITIES to get CPU performance information which is > exposed by it via sysfs and CPU performance scaling is based on it. > Thus using this information for setting asymmetric CPU capacity is > consistent with what the driver has been doing already. Moreover, > HWP_HIGHEST_PERF reflects the maximum capacity of a given CPU including > both the instructions-per-cycle (IPC) factor and the maximum turbo > frequency and the units in which that value is expressed are the same > for all CPUs in the system, so the maximum capacity ratio between two > CPUs can be obtained by computing the ratio of their HWP_HIGHEST_PERF > values. Of course, in principle that capacity ratio need not be > directly applicable at lower frequencies, so using it for providing the > asymmetric CPU capacity information to the scheduler is a rough > approximation, but it is as good as it gets. Also, measurements > indicate that this approximation is not too bad in practice. So cpu_capacity has a direct mapping to itmt prio. cpu_capacity is itmt prio with max itmt prio scaled to 1024. Running it on i7-13700K (while allowing SMT) gives: root@gulliver:~# dmesg | grep sched_set_itmt_core_prio [ 3.957826] sched_set_itmt_core_prio() cpu=0 prio=68 [ 3.990401] sched_set_itmt_core_prio() cpu=1 prio=68 [ 4.015551] sched_set_itmt_core_prio() cpu=2 prio=68 [ 4.040720] sched_set_itmt_core_prio() cpu=3 prio=68 [ 4.065871] sched_set_itmt_core_prio() cpu=4 prio=68 [ 4.091018] sched_set_itmt_core_prio() cpu=5 prio=68 [ 4.116175] sched_set_itmt_core_prio() cpu=6 prio=68 [ 4.141374] sched_set_itmt_core_prio() cpu=7 prio=68 [ 4.166543] sched_set_itmt_core_prio() cpu=8 prio=69 [ 4.196289] sched_set_itmt_core_prio() cpu=9 prio=69 [ 4.214964] sched_set_itmt_core_prio() cpu=10 prio=69 [ 4.239281] sched_set_itmt_core_prio() cpu=11 prio=69 [ 4.263438] sched_set_itmt_core_prio() cpu=12 prio=68 [ 4.283790] sched_set_itmt_core_prio() cpu=13 prio=68 [ 4.308905] sched_set_itmt_core_prio() cpu=14 prio=68 [ 4.331751] sched_set_itmt_core_prio() cpu=15 prio=68 [ 4.356002] sched_set_itmt_core_prio() cpu=16 prio=42 [ 4.381639] sched_set_itmt_core_prio() cpu=17 prio=42 [ 4.395175] sched_set_itmt_core_prio() cpu=18 prio=42 [ 4.425625] sched_set_itmt_core_prio() cpu=19 prio=42 [ 4.449670] sched_set_itmt_core_prio() cpu=20 prio=42 [ 4.479681] sched_set_itmt_core_prio() cpu=21 prio=42 [ 4.506319] sched_set_itmt_core_prio() cpu=22 prio=42 [ 4.523774] sched_set_itmt_core_prio() cpu=23 prio=42 root@gulliver:~# dmesg | grep hybrid_set_cpu_capacity [ 4.450883] hybrid_set_cpu_capacity() cpu=0 cap=1009 [ 4.455846] hybrid_set_cpu_capacity() cpu=1 cap=1009 [ 4.460806] hybrid_set_cpu_capacity() cpu=2 cap=1009 [ 4.465766] hybrid_set_cpu_capacity() cpu=3 cap=1009 [ 4.470730] hybrid_set_cpu_capacity() cpu=4 cap=1009 [ 4.475699] hybrid_set_cpu_capacity() cpu=5 cap=1009 [ 4.480664] hybrid_set_cpu_capacity() cpu=6 cap=1009 [ 4.485626] hybrid_set_cpu_capacity() cpu=7 cap=1009 [ 4.490588] hybrid_set_cpu_capacity() cpu=9 cap=1024 [ 4.495550] hybrid_set_cpu_capacity() cpu=10 cap=1024 [ 4.500598] hybrid_set_cpu_capacity() cpu=11 cap=1024 [ 4.505649] hybrid_set_cpu_capacity() cpu=12 cap=1009 [ 4.510701] hybrid_set_cpu_capacity() cpu=13 cap=1009 [ 4.515749] hybrid_set_cpu_capacity() cpu=14 cap=1009 [ 4.520802] hybrid_set_cpu_capacity() cpu=15 cap=1009 [ 4.525846] hybrid_set_cpu_capacity() cpu=16 cap=623 [ 4.530810] hybrid_set_cpu_capacity() cpu=17 cap=623 [ 4.535772] hybrid_set_cpu_capacity() cpu=18 cap=623 [ 4.540732] hybrid_set_cpu_capacity() cpu=19 cap=623 [ 4.545690] hybrid_set_cpu_capacity() cpu=20 cap=623 [ 4.550651] hybrid_set_cpu_capacity() cpu=21 cap=623 [ 4.555612] hybrid_set_cpu_capacity() cpu=22 cap=623 [ 4.560571] hybrid_set_cpu_capacity() cpu=23 cap=623 > If the given system is hybrid and non-SMT, the new code disables ITMT > support in the scheduler (because it may get in the way of asymmetric CPU > capacity code in the scheduler that automatically gets enabled by setting > asymmetric CPU capacity) after initializing all online CPUs and finds > the one with the maximum HWP_HIGHEST_PERF value. Next, it computes the > capacity number for each (online) CPU by dividing the product of its > HWP_HIGHEST_PERF and SCHED_CAPACITY_SCALE by the maximum HWP_HIGHEST_PERF. SO either CAS at wakeup and in load_balance or SIS at wakeup and ITMT in load balance. > When a CPU goes offline, its capacity is reset to SCHED_CAPACITY_SCALE > and if it is the one with the maximum HWP_HIGHEST_PERF value, the > capacity numbers for all of the other online CPUs are recomputed. This > also takes care of a cleanup during driver operation mode changes. > > Analogously, when a new CPU goes online, its capacity number is updated > and if its HWP_HIGHEST_PERF value is greater than the current maximum > one, the capacity numbers for all of the other online CPUs are > recomputed. > > The case when the driver is notified of a CPU capacity change, either > through the HWP interrupt or through an ACPI notification, is handled > similarly to the CPU online case above, except that if the target CPU > is the current highest-capacity one and its capacity is reduced, the > capacity numbers for all of the other online CPUs need to be recomputed > either. > > If the driver's "no_trubo" sysfs attribute is updated, all of the CPU > capacity information is computed from scratch to reflect the new turbo > status. So if I do: echo 1 > /sys/devices/system/cpu/intel_pstate/no_turbo I get: [ 1692.801368] hybrid_update_cpu_scaling() called [ 1692.801381] hybrid_update_cpu_scaling() max_cap_perf=44, max_perf_cpu=0 [ 1692.801389] hybrid_set_cpu_capacity() cpu=1 cap=1024 [ 1692.801395] hybrid_set_cpu_capacity() cpu=2 cap=1024 [ 1692.801399] hybrid_set_cpu_capacity() cpu=3 cap=1024 [ 1692.801402] hybrid_set_cpu_capacity() cpu=4 cap=1024 [ 1692.801405] hybrid_set_cpu_capacity() cpu=5 cap=1024 [ 1692.801408] hybrid_set_cpu_capacity() cpu=6 cap=1024 [ 1692.801410] hybrid_set_cpu_capacity() cpu=7 cap=1024 [ 1692.801413] hybrid_set_cpu_capacity() cpu=8 cap=1024 [ 1692.801416] hybrid_set_cpu_capacity() cpu=9 cap=1024 [ 1692.801419] hybrid_set_cpu_capacity() cpu=10 cap=1024 [ 1692.801422] hybrid_set_cpu_capacity() cpu=11 cap=1024 [ 1692.801425] hybrid_set_cpu_capacity() cpu=12 cap=1024 [ 1692.801428] hybrid_set_cpu_capacity() cpu=13 cap=1024 [ 1692.801431] hybrid_set_cpu_capacity() cpu=14 cap=1024 [ 1692.801433] hybrid_set_cpu_capacity() cpu=15 cap=1024 [ 1692.801436] hybrid_set_cpu_capacity() cpu=16 cap=605 [ 1692.801439] hybrid_set_cpu_capacity() cpu=17 cap=605 [ 1692.801442] hybrid_set_cpu_capacity() cpu=18 cap=605 [ 1692.801445] hybrid_set_cpu_capacity() cpu=19 cap=605 [ 1692.801448] hybrid_set_cpu_capacity() cpu=20 cap=605 [ 1692.801451] hybrid_set_cpu_capacity() cpu=21 cap=605 [ 1692.801453] hybrid_set_cpu_capacity() cpu=22 cap=605 [ 1692.801456] hybrid_set_cpu_capacity() cpu=23 cap=605 Turbo on this machine stands only for the cpu_capacity diff 1009 vs 1024? [...]
On Thu, May 02, 2024 at 12:42:54PM +0200, Dietmar Eggemann wrote: > On 25/04/2024 21:06, Rafael J. Wysocki wrote: > > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > > > Make intel_pstate use the HWP_HIGHEST_PERF values from > > MSR_HWP_CAPABILITIES to set asymmetric CPU capacity information > > via the previously introduced arch_set_cpu_capacity() on hybrid > > systems without SMT. > > Are there such systems around? My i7-13700K has P-cores (CPU0..CPU15) > with SMT. We have been experimenting with nosmt in the kernel command line. > > > Setting asymmetric CPU capacity is generally necessary to allow the > > scheduler to compute task sizes in a consistent way across all CPUs > > in a system where they differ by capacity. That, in turn, should help > > to improve task placement and load balancing decisions. It is also > > necessary for the schedutil cpufreq governor to operate as expected > > on hybrid systems where tasks migrate between CPUs of different > > capacities. > > > > The underlying observation is that intel_pstate already uses > > MSR_HWP_CAPABILITIES to get CPU performance information which is > > exposed by it via sysfs and CPU performance scaling is based on it. > > Thus using this information for setting asymmetric CPU capacity is > > consistent with what the driver has been doing already. Moreover, > > HWP_HIGHEST_PERF reflects the maximum capacity of a given CPU including > > both the instructions-per-cycle (IPC) factor and the maximum turbo > > frequency and the units in which that value is expressed are the same > > for all CPUs in the system, so the maximum capacity ratio between two > > CPUs can be obtained by computing the ratio of their HWP_HIGHEST_PERF > > values. Of course, in principle that capacity ratio need not be > > directly applicable at lower frequencies, so using it for providing the > > asymmetric CPU capacity information to the scheduler is a rough > > approximation, but it is as good as it gets. Also, measurements > > indicate that this approximation is not too bad in practice. > > So cpu_capacity has a direct mapping to itmt prio. cpu_capacity is itmt > prio with max itmt prio scaled to 1024. ITMT enables asym_packing in the load balancer. Since it only cares about which CPU has higher priority, scaling to 1024 is not necessary. > > Running it on i7-13700K (while allowing SMT) gives: > > root@gulliver:~# dmesg | grep sched_set_itmt_core_prio > [ 3.957826] sched_set_itmt_core_prio() cpu=0 prio=68 > [ 3.990401] sched_set_itmt_core_prio() cpu=1 prio=68 > [ 4.015551] sched_set_itmt_core_prio() cpu=2 prio=68 > [ 4.040720] sched_set_itmt_core_prio() cpu=3 prio=68 > [ 4.065871] sched_set_itmt_core_prio() cpu=4 prio=68 > [ 4.091018] sched_set_itmt_core_prio() cpu=5 prio=68 > [ 4.116175] sched_set_itmt_core_prio() cpu=6 prio=68 > [ 4.141374] sched_set_itmt_core_prio() cpu=7 prio=68 > [ 4.166543] sched_set_itmt_core_prio() cpu=8 prio=69 > [ 4.196289] sched_set_itmt_core_prio() cpu=9 prio=69 > [ 4.214964] sched_set_itmt_core_prio() cpu=10 prio=69 > [ 4.239281] sched_set_itmt_core_prio() cpu=11 prio=69 > [ 4.263438] sched_set_itmt_core_prio() cpu=12 prio=68 > [ 4.283790] sched_set_itmt_core_prio() cpu=13 prio=68 > [ 4.308905] sched_set_itmt_core_prio() cpu=14 prio=68 > [ 4.331751] sched_set_itmt_core_prio() cpu=15 prio=68 > [ 4.356002] sched_set_itmt_core_prio() cpu=16 prio=42 > [ 4.381639] sched_set_itmt_core_prio() cpu=17 prio=42 > [ 4.395175] sched_set_itmt_core_prio() cpu=18 prio=42 > [ 4.425625] sched_set_itmt_core_prio() cpu=19 prio=42 > [ 4.449670] sched_set_itmt_core_prio() cpu=20 prio=42 > [ 4.479681] sched_set_itmt_core_prio() cpu=21 prio=42 > [ 4.506319] sched_set_itmt_core_prio() cpu=22 prio=42 > [ 4.523774] sched_set_itmt_core_prio() cpu=23 prio=42 > > root@gulliver:~# dmesg | grep hybrid_set_cpu_capacity > [ 4.450883] hybrid_set_cpu_capacity() cpu=0 cap=1009 > [ 4.455846] hybrid_set_cpu_capacity() cpu=1 cap=1009 > [ 4.460806] hybrid_set_cpu_capacity() cpu=2 cap=1009 > [ 4.465766] hybrid_set_cpu_capacity() cpu=3 cap=1009 > [ 4.470730] hybrid_set_cpu_capacity() cpu=4 cap=1009 > [ 4.475699] hybrid_set_cpu_capacity() cpu=5 cap=1009 > [ 4.480664] hybrid_set_cpu_capacity() cpu=6 cap=1009 > [ 4.485626] hybrid_set_cpu_capacity() cpu=7 cap=1009 > [ 4.490588] hybrid_set_cpu_capacity() cpu=9 cap=1024 > [ 4.495550] hybrid_set_cpu_capacity() cpu=10 cap=1024 > [ 4.500598] hybrid_set_cpu_capacity() cpu=11 cap=1024 > [ 4.505649] hybrid_set_cpu_capacity() cpu=12 cap=1009 > [ 4.510701] hybrid_set_cpu_capacity() cpu=13 cap=1009 > [ 4.515749] hybrid_set_cpu_capacity() cpu=14 cap=1009 > [ 4.520802] hybrid_set_cpu_capacity() cpu=15 cap=1009 > [ 4.525846] hybrid_set_cpu_capacity() cpu=16 cap=623 > [ 4.530810] hybrid_set_cpu_capacity() cpu=17 cap=623 > [ 4.535772] hybrid_set_cpu_capacity() cpu=18 cap=623 > [ 4.540732] hybrid_set_cpu_capacity() cpu=19 cap=623 > [ 4.545690] hybrid_set_cpu_capacity() cpu=20 cap=623 > [ 4.550651] hybrid_set_cpu_capacity() cpu=21 cap=623 > [ 4.555612] hybrid_set_cpu_capacity() cpu=22 cap=623 > [ 4.560571] hybrid_set_cpu_capacity() cpu=23 cap=623 > > > If the given system is hybrid and non-SMT, the new code disables ITMT > > support in the scheduler (because it may get in the way of asymmetric CPU > > capacity code in the scheduler that automatically gets enabled by setting > > asymmetric CPU capacity) after initializing all online CPUs and finds > > the one with the maximum HWP_HIGHEST_PERF value. Next, it computes the > > capacity number for each (online) CPU by dividing the product of its > > HWP_HIGHEST_PERF and SCHED_CAPACITY_SCALE by the maximum HWP_HIGHEST_PERF. > > SO either CAS at wakeup and in load_balance or SIS at wakeup and ITMT in > load balance. May I know what CAS and SIS stand for? Thanks and BR, Ricardo
On 03/05/2024 05:32, Ricardo Neri wrote: > On Thu, May 02, 2024 at 12:42:54PM +0200, Dietmar Eggemann wrote: >> On 25/04/2024 21:06, Rafael J. Wysocki wrote: >>> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> >>> >>> Make intel_pstate use the HWP_HIGHEST_PERF values from >>> MSR_HWP_CAPABILITIES to set asymmetric CPU capacity information >>> via the previously introduced arch_set_cpu_capacity() on hybrid >>> systems without SMT. >> >> Are there such systems around? My i7-13700K has P-cores (CPU0..CPU15) >> with SMT. > > We have been experimenting with nosmt in the kernel command line. OK. [...] >>> If the given system is hybrid and non-SMT, the new code disables ITMT >>> support in the scheduler (because it may get in the way of asymmetric CPU >>> capacity code in the scheduler that automatically gets enabled by setting >>> asymmetric CPU capacity) after initializing all online CPUs and finds >>> the one with the maximum HWP_HIGHEST_PERF value. Next, it computes the >>> capacity number for each (online) CPU by dividing the product of its >>> HWP_HIGHEST_PERF and SCHED_CAPACITY_SCALE by the maximum HWP_HIGHEST_PERF. >> >> SO either CAS at wakeup and in load_balance or SIS at wakeup and ITMT in >> load balance. > > May I know what CAS and SIS stand for? Capacity Aware Scheduling and Select_Idle_Sibling(). Either select_idle_sibling() -> select_idle_capacity() (1) or select_idle_sibling() -> select_idle_cpu() /* nosmt */ (2) So my system with now 'nosmt' goes (1).
On Thu, May 2, 2024 at 12:43 PM Dietmar Eggemann <dietmar.eggemann@arm.com> wrote: > > On 25/04/2024 21:06, Rafael J. Wysocki wrote: > > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > > > Make intel_pstate use the HWP_HIGHEST_PERF values from > > MSR_HWP_CAPABILITIES to set asymmetric CPU capacity information > > via the previously introduced arch_set_cpu_capacity() on hybrid > > systems without SMT. > > Are there such systems around? My i7-13700K has P-cores (CPU0..CPU15) > with SMT. As Ricardo said, nosmt is one way to run without SMT. Another one is to disable SMT in the BIOS setup. Anyway, the point here is that with SMT, accurate tracking of task utilization is rather hopeless. > > Setting asymmetric CPU capacity is generally necessary to allow the > > scheduler to compute task sizes in a consistent way across all CPUs > > in a system where they differ by capacity. That, in turn, should help > > to improve task placement and load balancing decisions. It is also > > necessary for the schedutil cpufreq governor to operate as expected > > on hybrid systems where tasks migrate between CPUs of different > > capacities. > > > > The underlying observation is that intel_pstate already uses > > MSR_HWP_CAPABILITIES to get CPU performance information which is > > exposed by it via sysfs and CPU performance scaling is based on it. > > Thus using this information for setting asymmetric CPU capacity is > > consistent with what the driver has been doing already. Moreover, > > HWP_HIGHEST_PERF reflects the maximum capacity of a given CPU including > > both the instructions-per-cycle (IPC) factor and the maximum turbo > > frequency and the units in which that value is expressed are the same > > for all CPUs in the system, so the maximum capacity ratio between two > > CPUs can be obtained by computing the ratio of their HWP_HIGHEST_PERF > > values. Of course, in principle that capacity ratio need not be > > directly applicable at lower frequencies, so using it for providing the > > asymmetric CPU capacity information to the scheduler is a rough > > approximation, but it is as good as it gets. Also, measurements > > indicate that this approximation is not too bad in practice. > > So cpu_capacity has a direct mapping to itmt prio. cpu_capacity is itmt > prio with max itmt prio scaled to 1024. Right. The choice to make the ITMT prio reflect the capacity is deliberate, although this code works with values retrieved via CPPC (which are the same as the HWP_CAP values in the majority of cases but not always). > Running it on i7-13700K (while allowing SMT) gives: > > root@gulliver:~# dmesg | grep sched_set_itmt_core_prio > [ 3.957826] sched_set_itmt_core_prio() cpu=0 prio=68 > [ 3.990401] sched_set_itmt_core_prio() cpu=1 prio=68 > [ 4.015551] sched_set_itmt_core_prio() cpu=2 prio=68 > [ 4.040720] sched_set_itmt_core_prio() cpu=3 prio=68 > [ 4.065871] sched_set_itmt_core_prio() cpu=4 prio=68 > [ 4.091018] sched_set_itmt_core_prio() cpu=5 prio=68 > [ 4.116175] sched_set_itmt_core_prio() cpu=6 prio=68 > [ 4.141374] sched_set_itmt_core_prio() cpu=7 prio=68 > [ 4.166543] sched_set_itmt_core_prio() cpu=8 prio=69 > [ 4.196289] sched_set_itmt_core_prio() cpu=9 prio=69 > [ 4.214964] sched_set_itmt_core_prio() cpu=10 prio=69 > [ 4.239281] sched_set_itmt_core_prio() cpu=11 prio=69 CPUs 8 - 10 appear to be "favored cores" that can turbo up higher than the other P-cores. > [ 4.263438] sched_set_itmt_core_prio() cpu=12 prio=68 > [ 4.283790] sched_set_itmt_core_prio() cpu=13 prio=68 > [ 4.308905] sched_set_itmt_core_prio() cpu=14 prio=68 > [ 4.331751] sched_set_itmt_core_prio() cpu=15 prio=68 > [ 4.356002] sched_set_itmt_core_prio() cpu=16 prio=42 > [ 4.381639] sched_set_itmt_core_prio() cpu=17 prio=42 > [ 4.395175] sched_set_itmt_core_prio() cpu=18 prio=42 > [ 4.425625] sched_set_itmt_core_prio() cpu=19 prio=42 > [ 4.449670] sched_set_itmt_core_prio() cpu=20 prio=42 > [ 4.479681] sched_set_itmt_core_prio() cpu=21 prio=42 > [ 4.506319] sched_set_itmt_core_prio() cpu=22 prio=42 > [ 4.523774] sched_set_itmt_core_prio() cpu=23 prio=42 > > root@gulliver:~# dmesg | grep hybrid_set_cpu_capacity > [ 4.450883] hybrid_set_cpu_capacity() cpu=0 cap=1009 > [ 4.455846] hybrid_set_cpu_capacity() cpu=1 cap=1009 > [ 4.460806] hybrid_set_cpu_capacity() cpu=2 cap=1009 > [ 4.465766] hybrid_set_cpu_capacity() cpu=3 cap=1009 > [ 4.470730] hybrid_set_cpu_capacity() cpu=4 cap=1009 > [ 4.475699] hybrid_set_cpu_capacity() cpu=5 cap=1009 > [ 4.480664] hybrid_set_cpu_capacity() cpu=6 cap=1009 > [ 4.485626] hybrid_set_cpu_capacity() cpu=7 cap=1009 > [ 4.490588] hybrid_set_cpu_capacity() cpu=9 cap=1024 > [ 4.495550] hybrid_set_cpu_capacity() cpu=10 cap=1024 > [ 4.500598] hybrid_set_cpu_capacity() cpu=11 cap=1024 And the "favored cores" get the max capacity. > [ 4.505649] hybrid_set_cpu_capacity() cpu=12 cap=1009 > [ 4.510701] hybrid_set_cpu_capacity() cpu=13 cap=1009 > [ 4.515749] hybrid_set_cpu_capacity() cpu=14 cap=1009 > [ 4.520802] hybrid_set_cpu_capacity() cpu=15 cap=1009 > [ 4.525846] hybrid_set_cpu_capacity() cpu=16 cap=623 > [ 4.530810] hybrid_set_cpu_capacity() cpu=17 cap=623 > [ 4.535772] hybrid_set_cpu_capacity() cpu=18 cap=623 > [ 4.540732] hybrid_set_cpu_capacity() cpu=19 cap=623 > [ 4.545690] hybrid_set_cpu_capacity() cpu=20 cap=623 > [ 4.550651] hybrid_set_cpu_capacity() cpu=21 cap=623 > [ 4.555612] hybrid_set_cpu_capacity() cpu=22 cap=623 > [ 4.560571] hybrid_set_cpu_capacity() cpu=23 cap=623 > > > If the given system is hybrid and non-SMT, the new code disables ITMT > > support in the scheduler (because it may get in the way of asymmetric CPU > > capacity code in the scheduler that automatically gets enabled by setting > > asymmetric CPU capacity) after initializing all online CPUs and finds > > the one with the maximum HWP_HIGHEST_PERF value. Next, it computes the > > capacity number for each (online) CPU by dividing the product of its > > HWP_HIGHEST_PERF and SCHED_CAPACITY_SCALE by the maximum HWP_HIGHEST_PERF. > > SO either CAS at wakeup and in load_balance or SIS at wakeup and ITMT in > load balance. Yup, at least for this version of the patch. > > When a CPU goes offline, its capacity is reset to SCHED_CAPACITY_SCALE > > and if it is the one with the maximum HWP_HIGHEST_PERF value, the > > capacity numbers for all of the other online CPUs are recomputed. This > > also takes care of a cleanup during driver operation mode changes. > > > > Analogously, when a new CPU goes online, its capacity number is updated > > and if its HWP_HIGHEST_PERF value is greater than the current maximum > > one, the capacity numbers for all of the other online CPUs are > > recomputed. > > > > The case when the driver is notified of a CPU capacity change, either > > through the HWP interrupt or through an ACPI notification, is handled > > similarly to the CPU online case above, except that if the target CPU > > is the current highest-capacity one and its capacity is reduced, the > > capacity numbers for all of the other online CPUs need to be recomputed > > either. > > > > If the driver's "no_trubo" sysfs attribute is updated, all of the CPU > > capacity information is computed from scratch to reflect the new turbo > > status. > > So if I do: > > echo 1 > /sys/devices/system/cpu/intel_pstate/no_turbo > > I get: > > [ 1692.801368] hybrid_update_cpu_scaling() called > [ 1692.801381] hybrid_update_cpu_scaling() max_cap_perf=44, max_perf_cpu=0 > [ 1692.801389] hybrid_set_cpu_capacity() cpu=1 cap=1024 > [ 1692.801395] hybrid_set_cpu_capacity() cpu=2 cap=1024 > [ 1692.801399] hybrid_set_cpu_capacity() cpu=3 cap=1024 > [ 1692.801402] hybrid_set_cpu_capacity() cpu=4 cap=1024 > [ 1692.801405] hybrid_set_cpu_capacity() cpu=5 cap=1024 > [ 1692.801408] hybrid_set_cpu_capacity() cpu=6 cap=1024 > [ 1692.801410] hybrid_set_cpu_capacity() cpu=7 cap=1024 > [ 1692.801413] hybrid_set_cpu_capacity() cpu=8 cap=1024 > [ 1692.801416] hybrid_set_cpu_capacity() cpu=9 cap=1024 > [ 1692.801419] hybrid_set_cpu_capacity() cpu=10 cap=1024 > [ 1692.801422] hybrid_set_cpu_capacity() cpu=11 cap=1024 > [ 1692.801425] hybrid_set_cpu_capacity() cpu=12 cap=1024 > [ 1692.801428] hybrid_set_cpu_capacity() cpu=13 cap=1024 > [ 1692.801431] hybrid_set_cpu_capacity() cpu=14 cap=1024 > [ 1692.801433] hybrid_set_cpu_capacity() cpu=15 cap=1024 > [ 1692.801436] hybrid_set_cpu_capacity() cpu=16 cap=605 > [ 1692.801439] hybrid_set_cpu_capacity() cpu=17 cap=605 > [ 1692.801442] hybrid_set_cpu_capacity() cpu=18 cap=605 > [ 1692.801445] hybrid_set_cpu_capacity() cpu=19 cap=605 > [ 1692.801448] hybrid_set_cpu_capacity() cpu=20 cap=605 > [ 1692.801451] hybrid_set_cpu_capacity() cpu=21 cap=605 > [ 1692.801453] hybrid_set_cpu_capacity() cpu=22 cap=605 > [ 1692.801456] hybrid_set_cpu_capacity() cpu=23 cap=605 > > Turbo on this machine stands only for the cpu_capacity diff 1009 vs 1024? Not really. The capacity of the fastest CPU is always 1024 and the capacities of all of the other CPUs are adjusted to that. When turbo is disabled, the capacity of the "favored cores" is the same as for the other P-cores (i.e. 1024) and the capacity of E-cores is relative to that. Of course, this means that task placement may be somewhat messed up after disabling or enabling turbo (which is a global switch), but I don't think that there is a way to avoid it.
On 25/04/2024 21:06, Rafael J. Wysocki wrote: > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > Make intel_pstate use the HWP_HIGHEST_PERF values from > MSR_HWP_CAPABILITIES to set asymmetric CPU capacity information > via the previously introduced arch_set_cpu_capacity() on hybrid > systems without SMT. > > Setting asymmetric CPU capacity is generally necessary to allow the > scheduler to compute task sizes in a consistent way across all CPUs > in a system where they differ by capacity. That, in turn, should help > to improve task placement and load balancing decisions. It is also > necessary for the schedutil cpufreq governor to operate as expected > on hybrid systems where tasks migrate between CPUs of different > capacities. [...] For Arm64 we expose the cpu_capacity under: /sys/devices/system/cpu/cpu*/cpu_capacity Might be handy for X86 hybrid as well. Code snippet copied from from drivers/base/arch_topology.c : diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c index 9e94b3f05a57..c445e5d1efc8 100644 --- a/drivers/cpufreq/intel_pstate.c +++ b/drivers/cpufreq/intel_pstate.c @@ -3746,5 +3746,49 @@ static int __init intel_pstate_setup(char *str) } early_param("intel_pstate", intel_pstate_setup); +static ssize_t cpu_capacity_show(struct device *dev, + struct device_attribute *attr, + char *buf) +{ + struct cpu *cpu = container_of(dev, struct cpu, dev); + + return sysfs_emit(buf, "%lu\n", arch_scale_cpu_capacity(cpu->dev.id)); +} + +static DEVICE_ATTR_RO(cpu_capacity); + +static int cpu_capacity_sysctl_add(unsigned int cpu) +{ + struct device *cpu_dev = get_cpu_device(cpu); + + if (!cpu_dev) + return -ENOENT; + + device_create_file(cpu_dev, &dev_attr_cpu_capacity); + + return 0; +} + +static int cpu_capacity_sysctl_remove(unsigned int cpu) +{ + struct device *cpu_dev = get_cpu_device(cpu); + + if (!cpu_dev) + return -ENOENT; + + device_remove_file(cpu_dev, &dev_attr_cpu_capacity); + + return 0; +} + +static int register_cpu_capacity_sysctl(void) +{ + cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "topology/cpu-capacity", + cpu_capacity_sysctl_add, cpu_capacity_sysctl_remove); + + return 0; +} +subsys_initcall(register_cpu_capacity_sysctl); + [...]
Index: linux-pm/drivers/cpufreq/intel_pstate.c =================================================================== --- linux-pm.orig/drivers/cpufreq/intel_pstate.c +++ linux-pm/drivers/cpufreq/intel_pstate.c @@ -16,6 +16,7 @@ #include <linux/tick.h> #include <linux/slab.h> #include <linux/sched/cpufreq.h> +#include <linux/sched/smt.h> #include <linux/list.h> #include <linux/cpu.h> #include <linux/cpufreq.h> @@ -215,6 +216,7 @@ struct global_params { * @hwp_req_cached: Cached value of the last HWP Request MSR * @hwp_cap_cached: Cached value of the last HWP Capabilities MSR * @last_io_update: Last time when IO wake flag was set + * @capacity_perf: Perf from HWP_CAP used for capacity computations * @sched_flags: Store scheduler flags for possible cross CPU update * @hwp_boost_min: Last HWP boosted min performance * @suspended: Whether or not the driver has been suspended. @@ -253,6 +255,7 @@ struct cpudata { u64 hwp_req_cached; u64 hwp_cap_cached; u64 last_io_update; + unsigned int capacity_perf; unsigned int sched_flags; u32 hwp_boost_min; bool suspended; @@ -295,6 +298,7 @@ static int hwp_mode_bdw __ro_after_init; static bool per_cpu_limits __ro_after_init; static bool hwp_forced __ro_after_init; static bool hwp_boost __read_mostly; +static bool hwp_is_hybrid; static struct cpufreq_driver *intel_pstate_driver __read_mostly; @@ -934,6 +938,93 @@ static struct freq_attr *hwp_cpufreq_att NULL, }; +static struct cpudata *hybrid_max_perf_cpu __read_mostly; +/* + * This protects hybrid_max_perf_cpu, the @capacity_perf fields in struct + * cpudata, and the x86 arch capacity information from concurrent updates. + */ +static DEFINE_MUTEX(hybrid_capacity_lock); + +static unsigned int hybrid_get_cap_perf(struct cpudata *cpu) +{ + u64 hwp_cap = READ_ONCE(cpu->hwp_cap_cached); + + if (READ_ONCE(global.no_turbo)) + return HWP_GUARANTEED_PERF(hwp_cap); + + return HWP_HIGHEST_PERF(hwp_cap); +} + +static void hybrid_set_cpu_capacity(struct cpudata *cpu) +{ + u64 cap = div_u64((u64)SCHED_CAPACITY_SCALE * cpu->capacity_perf, + hybrid_max_perf_cpu->capacity_perf); + + arch_set_cpu_capacity(cpu->cpu, cap); +} + +static void hybrid_set_capacity_of_cpus(void) +{ + int cpunum; + + for_each_online_cpu(cpunum) { + struct cpudata *cpu = all_cpu_data[cpunum]; + + /* + * Skip hybrid_max_perf_cpu because its capacity is the + * maximum and need not be computed. + */ + if (cpu && cpu != hybrid_max_perf_cpu) + hybrid_set_cpu_capacity(cpu); + } +} + +static void hybrid_update_cpu_scaling(void) +{ + struct cpudata *max_perf_cpu = NULL; + unsigned int max_cap_perf = 0; + int cpunum; + + for_each_online_cpu(cpunum) { + struct cpudata *cpu = all_cpu_data[cpunum]; + unsigned int cap_perf; + + /* + * If hybrid_max_perf_cpu is not NULL at this point, it is + * being replaced, so skip it. + */ + if (!cpu || cpu == hybrid_max_perf_cpu) + continue; + + cap_perf = hybrid_get_cap_perf(cpu); + cpu->capacity_perf = cap_perf; + if (cap_perf > max_cap_perf) { + max_cap_perf = cap_perf; + max_perf_cpu = cpu; + } + } + + if (max_perf_cpu) { + arch_set_cpu_capacity(max_perf_cpu->cpu, SCHED_CAPACITY_SCALE); + hybrid_max_perf_cpu = max_perf_cpu; + hybrid_set_capacity_of_cpus(); + } else { + /* Revert to the flat CPU capacity structure. */ + for_each_online_cpu(cpunum) + arch_set_cpu_capacity(cpunum, SCHED_CAPACITY_SCALE); + } +} + +static void hybrid_init_cpu_scaling(void) +{ + mutex_lock(&hybrid_capacity_lock); + + hybrid_max_perf_cpu = NULL; + hybrid_update_cpu_scaling(); + + mutex_unlock(&hybrid_capacity_lock); +} + static void __intel_pstate_get_hwp_cap(struct cpudata *cpu) { u64 cap; @@ -962,6 +1053,40 @@ static void intel_pstate_get_hwp_cap(str } } +static void hybrid_update_capacity(struct cpudata *cpu) +{ + unsigned int max_cap_perf, cap_perf; + + mutex_lock(&hybrid_capacity_lock); + + if (!hybrid_max_perf_cpu) + goto unlock; + + max_cap_perf = hybrid_max_perf_cpu->capacity_perf; + + intel_pstate_get_hwp_cap(cpu); + + cap_perf = hybrid_get_cap_perf(cpu); + cpu->capacity_perf = cap_perf; + + if (cap_perf > max_cap_perf) { + arch_set_cpu_capacity(cpu->cpu, SCHED_CAPACITY_SCALE); + hybrid_max_perf_cpu = cpu; + hybrid_set_capacity_of_cpus(); + goto unlock; + } + + if (cpu == hybrid_max_perf_cpu && cap_perf < max_cap_perf) { + hybrid_update_cpu_scaling(); + goto unlock; + } + + hybrid_set_cpu_capacity(cpu); + +unlock: + mutex_unlock(&hybrid_capacity_lock); +} + static void intel_pstate_hwp_set(unsigned int cpu) { struct cpudata *cpu_data = all_cpu_data[cpu]; @@ -1070,6 +1195,16 @@ static void intel_pstate_hwp_offline(str value |= HWP_ENERGY_PERF_PREFERENCE(HWP_EPP_POWERSAVE); wrmsrl_on_cpu(cpu->cpu, MSR_HWP_REQUEST, value); + + mutex_lock(&hybrid_capacity_lock); + + if (hybrid_max_perf_cpu == cpu) + hybrid_update_cpu_scaling(); + + mutex_unlock(&hybrid_capacity_lock); + + /* Reset the capacity of the CPU going offline to the initial value. */ + arch_set_cpu_capacity(cpu->cpu, SCHED_CAPACITY_SCALE); } #define POWER_CTL_EE_ENABLE 1 @@ -1164,21 +1299,41 @@ static void __intel_pstate_update_max_fr static void intel_pstate_update_limits(unsigned int cpu) { struct cpufreq_policy *policy = cpufreq_cpu_acquire(cpu); + struct cpudata *cpudata; if (!policy) return; - __intel_pstate_update_max_freq(all_cpu_data[cpu], policy); + cpudata = all_cpu_data[cpu]; + + __intel_pstate_update_max_freq(cpudata, policy); + + /* Prevent the driver from being unregistered now. */ + mutex_lock(&intel_pstate_driver_lock); cpufreq_cpu_release(policy); + + hybrid_update_capacity(cpudata); + + mutex_unlock(&intel_pstate_driver_lock); } static void intel_pstate_update_limits_for_all(void) { int cpu; - for_each_possible_cpu(cpu) - intel_pstate_update_limits(cpu); + for_each_possible_cpu(cpu) { + struct cpufreq_policy *policy = cpufreq_cpu_acquire(cpu); + + if (!policy) + continue; + + __intel_pstate_update_max_freq(all_cpu_data[cpu], policy); + + cpufreq_cpu_release(policy); + } + + hybrid_init_cpu_scaling(); } /************************** sysfs begin ************************/ @@ -1612,6 +1767,13 @@ static void intel_pstate_notify_work(str __intel_pstate_update_max_freq(cpudata, policy); cpufreq_cpu_release(policy); + + /* + * The driver will not be unregistered while this function is + * running, so update the capacity without acquiring the driver + * lock. + */ + hybrid_update_capacity(cpudata); } wrmsrl_on_cpu(cpudata->cpu, MSR_HWP_STATUS, 0); @@ -2013,8 +2175,10 @@ static void intel_pstate_get_cpu_pstates if (pstate_funcs.get_cpu_scaling) { cpu->pstate.scaling = pstate_funcs.get_cpu_scaling(cpu->cpu); - if (cpu->pstate.scaling != perf_ctl_scaling) + if (cpu->pstate.scaling != perf_ctl_scaling) { intel_pstate_hybrid_hwp_adjust(cpu); + hwp_is_hybrid = true; + } } else { cpu->pstate.scaling = perf_ctl_scaling; } @@ -2682,6 +2846,8 @@ static int intel_pstate_cpu_online(struc */ intel_pstate_hwp_reenable(cpu); cpu->suspended = false; + + hybrid_update_capacity(cpu); } return 0; @@ -3124,6 +3290,19 @@ static int intel_pstate_register_driver( global.min_perf_pct = min_perf_pct_min(); + /* + * On hybrid systems, use asym capacity instead of ITMT, but because + * the capacity of SMT threads is not deterministic even approximately, + * do not do that when SMT is in use. + */ + if (hwp_is_hybrid && !sched_smt_active()) { + sched_clear_itmt_support(); + + hybrid_init_cpu_scaling(); + + arch_rebuild_sched_domains(); + } + return 0; }