| Mark Langsdorf | a2fed57 | 2010-03-18 18:41:46 +0100 | [diff] [blame] | 1 | #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 | |
| 10 | static DEFINE_PER_CPU(struct aperfmperf, acfreq_old_perf); |
| 11 | |
| 12 | /* Called via smp_call_function_single(), on the target CPU */ |
| 13 | static 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 | */ |
| 33 | unsigned 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 | } |
| 50 | EXPORT_SYMBOL_GPL(cpufreq_get_measured_perf); |
| 51 | MODULE_LICENSE("GPL"); |