Messages in this thread | ![/](/images/icornerl.gif) | | Date | Mon, 11 Mar 2024 11:27:27 -0700 | From | Vanshidhar Konda <> | Subject | Re: Re: [PATCH v1 2/3] arm64: idle: Cache AMU counters before entering idle |
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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/ >
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