Re: [patch 08/10] x86/aperfmperf: Store aperf/mperf data for cpu frequency reads

Rafael J. Wysocki
2022-04-19T16:31:03Z

On Fri, Apr 15, 2022 at 9:20 PM Thomas Gleixner <tglx@linutronix.de> wrote:
>
> Now that the MSR readout is unconditional, store the results in the per CPU
> data structure along with a jiffies timestamp for the CPU frequency readout
> code.
>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

> ---
> arch/x86/kernel/cpu/aperfmperf.c | 14 +++++++++++++-
> 1 file changed, 13 insertions(+), 1 deletion(-)
>
> --- a/arch/x86/kernel/cpu/aperfmperf.c
> +++ b/arch/x86/kernel/cpu/aperfmperf.c
> @@ -24,11 +24,17 @@
> #include "cpu.h"
>
> struct aperfmperf {
> + seqcount_t seq;
> + unsigned long last_update;
> + u64 acnt;
> + u64 mcnt;
> u64 aperf;
> u64 mperf;
> };
>
> -static DEFINE_PER_CPU_SHARED_ALIGNED(struct aperfmperf, cpu_samples);
> +static DEFINE_PER_CPU_SHARED_ALIGNED(struct aperfmperf, cpu_samples) = {
> + .seq = SEQCNT_ZERO(cpu_samples.seq)
> +};
>
> struct aperfmperf_sample {
> unsigned int khz;
> @@ -515,6 +521,12 @@ void arch_scale_freq_tick(void)
> s->aperf = aperf;
> s->mperf = mperf;
>
> + raw_write_seqcount_begin(&s->seq);
> + s->last_update = jiffies;
> + s->acnt = acnt;
> + s->mcnt = mcnt;
> + raw_write_seqcount_end(&s->seq);
> +
> scale_freq_tick(acnt, mcnt);
> }
>
>