| Message ID | 20240229162520.970986-3-vanshikonda@os.amperecomputing.com |
|---|---|
| State | New |
| Headers | show |
| Series | arm64: Use AMU counters for measuring CPU frequency | expand |
On Thu, Mar 07, 2024 at 11:17:26AM +0800, lihuisong (C) wrote: > >在 2024/3/1 0:25, Vanshidhar Konda 写道: >>AMU counters do not increment while a CPU is in idle. Saving the value >>of the core and constant counters prior to invoking WFI allows FIE to >>compute the frequency of a CPU that is idle. >> >>Signed-off-by: Vanshidhar Konda <vanshikonda@os.amperecomputing.com> >>--- >> arch/arm64/kernel/idle.c | 10 ++++++++++ >> arch/arm64/kernel/topology.c | 14 ++++++++------ >> 2 files changed, 18 insertions(+), 6 deletions(-) >> >>diff --git a/arch/arm64/kernel/idle.c b/arch/arm64/kernel/idle.c >>index 05cfb347ec26..5ed2e57188a8 100644 >>--- a/arch/arm64/kernel/idle.c >>+++ b/arch/arm64/kernel/idle.c >>@@ -26,6 +26,16 @@ void __cpuidle cpu_do_idle(void) >> arm_cpuidle_save_irq_context(&context); >>+#ifdef CONFIG_ARM64_AMU_EXTN >>+ /* Update the AMU counters before entering WFI. The cached AMU counter >>+ * value is used to determine CPU frequency while the CPU is idle >>+ * without needing to wake up the CPU. >>+ */ >>+ >>+ if (cpu_has_amu_feat(smp_processor_id())) >>+ update_freq_counters_refs(); >>+#endif >The below point I has mentioned in [1]. >This is just for the WFI state. >What about other deeper idle states, like retention and power down? >The path to enter idle state is different for them. We should do this >for all idle states. > Yes. That makes sense. I'll account for them in the next version of the patch. I'll work on the next version of the patch based on the updated patch from @Beata. Thanks, Vanshi >>+ >> dsb(sy); >> wfi(); >>diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c >>index db8d14525cf4..8905eb0c681f 100644 >>--- a/arch/arm64/kernel/topology.c >>+++ b/arch/arm64/kernel/topology.c >>@@ -240,13 +240,15 @@ unsigned int arch_freq_get_on_cpu(int cpu) >> } while (read_seqcount_retry(&cpu_sample->seq, seq)); >> /* >>- * Bail on invalid count and when the last update was too long ago, >>- * which covers idle and NOHZ full CPUs. >>+ * Bail on invalid count and when the last update was too long ago. >>+ * This covers idle, NOHZ full and isolated CPUs. >>+ * >>+ * Idle CPUs don't need to be measured because AMU counters stop >>+ * incrementing during WFI/WFE. >> */ >>- if (!delta_const_cnt || ((jiffies - last) > MAX_SAMPLE_AGE)) { >>- if (!(housekeeping_cpu(cpu, HK_TYPE_TICK) && idle_cpu(cpu))) >>- goto fallback; >>- } >>+ if (!delta_const_cnt || >>+ ((jiffies - last) > MAX_SAMPLE_AGE && !idle_cpu(cpu))) >>+ goto fallback; >> /* >> * CPU frequency = reference perf (in Hz) * (/\ delivered) / (/\ reference) >[1] https://lore.kernel.org/linux-arm-kernel/20231212072617.14756-1-lihuisong@huawei.com/ >
On Mon, Mar 11, 2024 at 11:27:27AM -0700, Vanshidhar Konda wrote: > On Thu, Mar 07, 2024 at 11:17:26AM +0800, lihuisong (C) wrote: > > > > 在 2024/3/1 0:25, Vanshidhar Konda 写道: > > > AMU counters do not increment while a CPU is in idle. Saving the value > > > of the core and constant counters prior to invoking WFI allows FIE to > > > compute the frequency of a CPU that is idle. > > > > > > Signed-off-by: Vanshidhar Konda <vanshikonda@os.amperecomputing.com> > > > --- > > > arch/arm64/kernel/idle.c | 10 ++++++++++ > > > arch/arm64/kernel/topology.c | 14 ++++++++------ > > > 2 files changed, 18 insertions(+), 6 deletions(-) > > > > > > diff --git a/arch/arm64/kernel/idle.c b/arch/arm64/kernel/idle.c > > > index 05cfb347ec26..5ed2e57188a8 100644 > > > --- a/arch/arm64/kernel/idle.c > > > +++ b/arch/arm64/kernel/idle.c > > > @@ -26,6 +26,16 @@ void __cpuidle cpu_do_idle(void) > > > arm_cpuidle_save_irq_context(&context); > > > +#ifdef CONFIG_ARM64_AMU_EXTN > > > + /* Update the AMU counters before entering WFI. The cached AMU counter > > > + * value is used to determine CPU frequency while the CPU is idle > > > + * without needing to wake up the CPU. > > > + */ > > > + > > > + if (cpu_has_amu_feat(smp_processor_id())) > > > + update_freq_counters_refs(); > > > +#endif > > The below point I has mentioned in [1]. > > This is just for the WFI state. > > What about other deeper idle states, like retention and power down? > > The path to enter idle state is different for them. We should do this > > for all idle states. > > > > Yes. That makes sense. I'll account for them in the next version of the > patch. I'll work on the next version of the patch based on the updated > patch from @Beata. > This should now be covered by [1] --- [1]https://lore.kernel.org/all/20240312083431.3239989-4-beata.michalska@arm.com/ --- BR Beata > Thanks, > Vanshi > > > > + > > > dsb(sy); > > > wfi(); > > > diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c > > > index db8d14525cf4..8905eb0c681f 100644 > > > --- a/arch/arm64/kernel/topology.c > > > +++ b/arch/arm64/kernel/topology.c > > > @@ -240,13 +240,15 @@ unsigned int arch_freq_get_on_cpu(int cpu) > > > } while (read_seqcount_retry(&cpu_sample->seq, seq)); > > > /* > > > - * Bail on invalid count and when the last update was too long ago, > > > - * which covers idle and NOHZ full CPUs. > > > + * Bail on invalid count and when the last update was too long ago. > > > + * This covers idle, NOHZ full and isolated CPUs. > > > + * > > > + * Idle CPUs don't need to be measured because AMU counters stop > > > + * incrementing during WFI/WFE. > > > */ > > > - if (!delta_const_cnt || ((jiffies - last) > MAX_SAMPLE_AGE)) { > > > - if (!(housekeeping_cpu(cpu, HK_TYPE_TICK) && idle_cpu(cpu))) > > > - goto fallback; > > > - } > > > + if (!delta_const_cnt || > > > + ((jiffies - last) > MAX_SAMPLE_AGE && !idle_cpu(cpu))) > > > + goto fallback; > > > /* > > > * CPU frequency = reference perf (in Hz) * (/\ delivered) / (/\ reference) > > [1] https://lore.kernel.org/linux-arm-kernel/20231212072617.14756-1-lihuisong@huawei.com/ > >
diff --git a/arch/arm64/kernel/idle.c b/arch/arm64/kernel/idle.c index 05cfb347ec26..5ed2e57188a8 100644 --- a/arch/arm64/kernel/idle.c +++ b/arch/arm64/kernel/idle.c @@ -26,6 +26,16 @@ void __cpuidle cpu_do_idle(void) arm_cpuidle_save_irq_context(&context); +#ifdef CONFIG_ARM64_AMU_EXTN + /* Update the AMU counters before entering WFI. The cached AMU counter + * value is used to determine CPU frequency while the CPU is idle + * without needing to wake up the CPU. + */ + + if (cpu_has_amu_feat(smp_processor_id())) + update_freq_counters_refs(); +#endif + dsb(sy); wfi(); diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c index db8d14525cf4..8905eb0c681f 100644 --- a/arch/arm64/kernel/topology.c +++ b/arch/arm64/kernel/topology.c @@ -240,13 +240,15 @@ unsigned int arch_freq_get_on_cpu(int cpu) } while (read_seqcount_retry(&cpu_sample->seq, seq)); /* - * Bail on invalid count and when the last update was too long ago, - * which covers idle and NOHZ full CPUs. + * Bail on invalid count and when the last update was too long ago. + * This covers idle, NOHZ full and isolated CPUs. + * + * Idle CPUs don't need to be measured because AMU counters stop + * incrementing during WFI/WFE. */ - if (!delta_const_cnt || ((jiffies - last) > MAX_SAMPLE_AGE)) { - if (!(housekeeping_cpu(cpu, HK_TYPE_TICK) && idle_cpu(cpu))) - goto fallback; - } + if (!delta_const_cnt || + ((jiffies - last) > MAX_SAMPLE_AGE && !idle_cpu(cpu))) + goto fallback; /* * CPU frequency = reference perf (in Hz) * (/\ delivered) / (/\ reference)
AMU counters do not increment while a CPU is in idle. Saving the value of the core and constant counters prior to invoking WFI allows FIE to compute the frequency of a CPU that is idle. Signed-off-by: Vanshidhar Konda <vanshikonda@os.amperecomputing.com> --- arch/arm64/kernel/idle.c | 10 ++++++++++ arch/arm64/kernel/topology.c | 14 ++++++++------ 2 files changed, 18 insertions(+), 6 deletions(-)