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

[Peter Zijlstra]

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));
> +}