mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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ea0ee33988
This reverts commit 941f5f0f6e.
Sadly, it turns out that we really can't just do the cross-CPU IPI to
all CPU's to get their proper frequencies, because it's much too
expensive on systems with lots of cores.
So we'll have to revert this for now, and revisit it using a smarter
model (probably doing one system-wide IPI at open time, and doing all
the frequency calculations in parallel).
Reported-by: WANG Chao <chao.wang@ucloud.cn>
Reported-by: Ingo Molnar <mingo@kernel.org>
Cc: Rafael J Wysocki <rafael.j.wysocki@intel.com>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
95 lines
2.1 KiB
C
95 lines
2.1 KiB
C
/*
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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 <len.brown@intel.com>
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*
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* This file is licensed under GPLv2.
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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/smp.h>
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struct aperfmperf_sample {
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unsigned int khz;
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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 20
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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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ktime_t now = ktime_get();
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s64 time_delta = ktime_ms_delta(now, s->time);
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unsigned long flags;
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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;
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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 = now;
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s->aperf = aperf;
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s->mperf = mperf;
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/* If the previous iteration was too long ago, discard it. */
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if (time_delta > APERFMPERF_STALE_THRESHOLD_MS)
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s->khz = 0;
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else
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s->khz = div64_u64((cpu_khz * aperf_delta), mperf_delta);
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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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unsigned int khz;
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if (!cpu_khz)
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return 0;
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if (!static_cpu_has(X86_FEATURE_APERFMPERF))
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return 0;
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smp_call_function_single(cpu, aperfmperf_snapshot_khz, NULL, 1);
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khz = per_cpu(samples.khz, cpu);
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if (khz)
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return khz;
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msleep(APERFMPERF_REFRESH_DELAY_MS);
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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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