Re: [PATCH 6/6] cpufreq: schedutil: New governor based on scheduler utilization data

Peter Zijlstra
2016-03-03T16:42:11Z

On Thu, Mar 03, 2016 at 05:28:29PM +0100, Peter Zijlstra wrote:
> +void arch_scale_freq_tick(void)
> +{
> + u64 aperf, mperf;
> + u64 acnt, mcnt;
> +
> + if (!static_cpu_has(X86_FEATURE_APERFMPERF))
> + return;
> +
> + aperf = rdmsrl(MSR_IA32_APERF);
> + mperf = rdmsrl(MSR_IA32_APERF);

Actually reading MPERF increases the chances of this working.

> +
> + acnt = aperf - this_cpu_read(arch_prev_aperf);
> + mcnt = mperf - this_cpu_read(arch_prev_mperf);
> +
> + this_cpu_write(arch_prev_aperf, aperf);
> + this_cpu_write(arch_prev_mperf, mperf);
> +
> + this_cpu_write(arch_cpu_freq, div64_u64(acnt * SCHED_CAPACITY_SCALE, mcnt));
> +}