blob: 911e193018aeb055bb8223683110714bfd017f83 [file] [log] [blame]
Mark Langsdorfa2fed572010-03-18 18:41:46 +01001#include <linux/kernel.h>
2#include <linux/smp.h>
3#include <linux/module.h>
4#include <linux/init.h>
5#include <linux/cpufreq.h>
6#include <linux/slab.h>
7
8#include "mperf.h"
9
10static DEFINE_PER_CPU(struct aperfmperf, acfreq_old_perf);
11
12/* Called via smp_call_function_single(), on the target CPU */
13static void read_measured_perf_ctrs(void *_cur)
14{
15 struct aperfmperf *am = _cur;
16
17 get_aperfmperf(am);
18}
19
20/*
21 * Return the measured active (C0) frequency on this CPU since last call
22 * to this function.
23 * Input: cpu number
24 * Return: Average CPU frequency in terms of max frequency (zero on error)
25 *
26 * We use IA32_MPERF and IA32_APERF MSRs to get the measured performance
27 * over a period of time, while CPU is in C0 state.
28 * IA32_MPERF counts at the rate of max advertised frequency
29 * IA32_APERF counts at the rate of actual CPU frequency
30 * Only IA32_APERF/IA32_MPERF ratio is architecturally defined and
31 * no meaning should be associated with absolute values of these MSRs.
32 */
33unsigned int cpufreq_get_measured_perf(struct cpufreq_policy *policy,
34 unsigned int cpu)
35{
36 struct aperfmperf perf;
37 unsigned long ratio;
38 unsigned int retval;
39
40 if (smp_call_function_single(cpu, read_measured_perf_ctrs, &perf, 1))
41 return 0;
42
43 ratio = calc_aperfmperf_ratio(&per_cpu(acfreq_old_perf, cpu), &perf);
44 per_cpu(acfreq_old_perf, cpu) = perf;
45
46 retval = (policy->cpuinfo.max_freq * ratio) >> APERFMPERF_SHIFT;
47
48 return retval;
49}
50EXPORT_SYMBOL_GPL(cpufreq_get_measured_perf);
51MODULE_LICENSE("GPL");