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151 lines
3.4 KiB
151 lines
3.4 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* x86 APERF/MPERF KHz calculation for |
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* /sys/.../cpufreq/scaling_cur_freq |
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* |
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* Copyright (C) 2017 Intel Corp. |
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* Author: Len Brown <[email protected]> |
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*/ |
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#include <linux/delay.h> |
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#include <linux/ktime.h> |
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#include <linux/math64.h> |
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#include <linux/percpu.h> |
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#include <linux/cpufreq.h> |
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#include <linux/smp.h> |
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#include <linux/sched/isolation.h> |
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#include <linux/rcupdate.h> |
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#include "cpu.h" |
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struct aperfmperf_sample { |
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unsigned int khz; |
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atomic_t scfpending; |
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ktime_t time; |
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u64 aperf; |
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u64 mperf; |
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}; |
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static DEFINE_PER_CPU(struct aperfmperf_sample, samples); |
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#define APERFMPERF_CACHE_THRESHOLD_MS 10 |
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#define APERFMPERF_REFRESH_DELAY_MS 10 |
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#define APERFMPERF_STALE_THRESHOLD_MS 1000 |
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/* |
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* aperfmperf_snapshot_khz() |
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* On the current CPU, snapshot APERF, MPERF, and jiffies |
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* unless we already did it within 10ms |
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* calculate kHz, save snapshot |
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*/ |
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static void aperfmperf_snapshot_khz(void *dummy) |
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{ |
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u64 aperf, aperf_delta; |
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u64 mperf, mperf_delta; |
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struct aperfmperf_sample *s = this_cpu_ptr(&samples); |
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unsigned long flags; |
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local_irq_save(flags); |
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rdmsrl(MSR_IA32_APERF, aperf); |
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rdmsrl(MSR_IA32_MPERF, mperf); |
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local_irq_restore(flags); |
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aperf_delta = aperf - s->aperf; |
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mperf_delta = mperf - s->mperf; |
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/* |
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* There is no architectural guarantee that MPERF |
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* increments faster than we can read it. |
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*/ |
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if (mperf_delta == 0) |
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return; |
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s->time = ktime_get(); |
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s->aperf = aperf; |
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s->mperf = mperf; |
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s->khz = div64_u64((cpu_khz * aperf_delta), mperf_delta); |
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atomic_set_release(&s->scfpending, 0); |
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} |
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static bool aperfmperf_snapshot_cpu(int cpu, ktime_t now, bool wait) |
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{ |
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s64 time_delta = ktime_ms_delta(now, per_cpu(samples.time, cpu)); |
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struct aperfmperf_sample *s = per_cpu_ptr(&samples, cpu); |
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/* Don't bother re-computing within the cache threshold time. */ |
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if (time_delta < APERFMPERF_CACHE_THRESHOLD_MS) |
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return true; |
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if (!atomic_xchg(&s->scfpending, 1) || wait) |
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smp_call_function_single(cpu, aperfmperf_snapshot_khz, NULL, wait); |
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/* Return false if the previous iteration was too long ago. */ |
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return time_delta <= APERFMPERF_STALE_THRESHOLD_MS; |
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} |
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unsigned int aperfmperf_get_khz(int cpu) |
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{ |
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if (!cpu_khz) |
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return 0; |
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if (!boot_cpu_has(X86_FEATURE_APERFMPERF)) |
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return 0; |
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if (!housekeeping_cpu(cpu, HK_FLAG_MISC)) |
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return 0; |
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if (rcu_is_idle_cpu(cpu)) |
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return 0; /* Idle CPUs are completely uninteresting. */ |
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aperfmperf_snapshot_cpu(cpu, ktime_get(), true); |
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return per_cpu(samples.khz, cpu); |
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} |
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void arch_freq_prepare_all(void) |
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{ |
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ktime_t now = ktime_get(); |
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bool wait = false; |
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int cpu; |
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if (!cpu_khz) |
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return; |
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if (!boot_cpu_has(X86_FEATURE_APERFMPERF)) |
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return; |
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for_each_online_cpu(cpu) { |
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if (!housekeeping_cpu(cpu, HK_FLAG_MISC)) |
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continue; |
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if (rcu_is_idle_cpu(cpu)) |
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continue; /* Idle CPUs are completely uninteresting. */ |
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if (!aperfmperf_snapshot_cpu(cpu, now, false)) |
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wait = true; |
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} |
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if (wait) |
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msleep(APERFMPERF_REFRESH_DELAY_MS); |
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} |
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unsigned int arch_freq_get_on_cpu(int cpu) |
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{ |
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struct aperfmperf_sample *s = per_cpu_ptr(&samples, cpu); |
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if (!cpu_khz) |
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return 0; |
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if (!boot_cpu_has(X86_FEATURE_APERFMPERF)) |
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return 0; |
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if (!housekeeping_cpu(cpu, HK_FLAG_MISC)) |
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return 0; |
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if (aperfmperf_snapshot_cpu(cpu, ktime_get(), true)) |
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return per_cpu(samples.khz, cpu); |
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msleep(APERFMPERF_REFRESH_DELAY_MS); |
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atomic_set(&s->scfpending, 1); |
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smp_mb(); /* ->scfpending before smp_call_function_single(). */ |
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smp_call_function_single(cpu, aperfmperf_snapshot_khz, NULL, 1); |
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return per_cpu(samples.khz, cpu); |
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}
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