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Date: Thu, 3 Mar 2016 17:42:05 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Vincent Guittot <vincent.guittot@...aro.org>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>,
"Rafael J. Wysocki" <rjw@...ysocki.net>,
Linux PM list <linux-pm@...r.kernel.org>,
Juri Lelli <juri.lelli@....com>,
Steve Muckle <steve.muckle@...aro.org>,
ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
Viresh Kumar <viresh.kumar@...aro.org>,
Michael Turquette <mturquette@...libre.com>
Subject: Re: [PATCH 6/6] cpufreq: schedutil: New governor based on scheduler
utilization data
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));
> +}
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