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authorRafael J. Wysocki <rafael.j.wysocki@intel.com>2017-11-15 02:13:40 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-01-10 09:31:20 +0100
commit22af48be826c4193bba2f11112330aabb2568594 (patch)
tree81755b76cb599e25c193ecc4783273ea9132c776
parenteff3e4fde76492931a45e23767c7842524b0ea06 (diff)
x86 / CPU: Always show current CPU frequency in /proc/cpuinfo
commit 7d5905dc14a87805a59f3c5bf70173aac2bb18f8 upstream. After commit 890da9cf0983 (Revert "x86: do not use cpufreq_quick_get() for /proc/cpuinfo "cpu MHz"") the "cpu MHz" number in /proc/cpuinfo on x86 can be either the nominal CPU frequency (which is constant) or the frequency most recently requested by a scaling governor in cpufreq, depending on the cpufreq configuration. That is somewhat inconsistent and is different from what it was before 4.13, so in order to restore the previous behavior, make it report the current CPU frequency like the scaling_cur_freq sysfs file in cpufreq. To that end, modify the /proc/cpuinfo implementation on x86 to use aperfmperf_snapshot_khz() to snapshot the APERF and MPERF feedback registers, if available, and use their values to compute the CPU frequency to be reported as "cpu MHz". However, do that carefully enough to avoid accumulating delays that lead to unacceptable access times for /proc/cpuinfo on systems with many CPUs. Run aperfmperf_snapshot_khz() once on all CPUs asynchronously at the /proc/cpuinfo open time, add a single delay upfront (if necessary) at that point and simply compute the current frequency while running show_cpuinfo() for each individual CPU. Also, to avoid slowing down /proc/cpuinfo accesses too much, reduce the default delay between consecutive APERF and MPERF reads to 10 ms, which should be sufficient to get large enough numbers for the frequency computation in all cases. Fixes: 890da9cf0983 (Revert "x86: do not use cpufreq_quick_get() for /proc/cpuinfo "cpu MHz"") Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Acked-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--arch/x86/kernel/cpu/Makefile2
-rw-r--r--arch/x86/kernel/cpu/aperfmperf.c74
-rw-r--r--arch/x86/kernel/cpu/cpu.h3
-rw-r--r--arch/x86/kernel/cpu/proc.c6
-rw-r--r--fs/proc/cpuinfo.c6
-rw-r--r--include/linux/cpufreq.h1
6 files changed, 68 insertions, 24 deletions
diff --git a/arch/x86/kernel/cpu/Makefile b/arch/x86/kernel/cpu/Makefile
index 90cb82dbba57..570e8bb1f386 100644
--- a/arch/x86/kernel/cpu/Makefile
+++ b/arch/x86/kernel/cpu/Makefile
@@ -22,7 +22,7 @@ obj-y += common.o
obj-y += rdrand.o
obj-y += match.o
obj-y += bugs.o
-obj-$(CONFIG_CPU_FREQ) += aperfmperf.o
+obj-y += aperfmperf.o
obj-y += cpuid-deps.o
obj-$(CONFIG_PROC_FS) += proc.o
diff --git a/arch/x86/kernel/cpu/aperfmperf.c b/arch/x86/kernel/cpu/aperfmperf.c
index 957813e0180d..7eba34df54c3 100644
--- a/arch/x86/kernel/cpu/aperfmperf.c
+++ b/arch/x86/kernel/cpu/aperfmperf.c
@@ -14,6 +14,8 @@
#include <linux/percpu.h>
#include <linux/smp.h>
+#include "cpu.h"
+
struct aperfmperf_sample {
unsigned int khz;
ktime_t time;
@@ -24,7 +26,7 @@ struct aperfmperf_sample {
static DEFINE_PER_CPU(struct aperfmperf_sample, samples);
#define APERFMPERF_CACHE_THRESHOLD_MS 10
-#define APERFMPERF_REFRESH_DELAY_MS 20
+#define APERFMPERF_REFRESH_DELAY_MS 10
#define APERFMPERF_STALE_THRESHOLD_MS 1000
/*
@@ -38,8 +40,6 @@ static void aperfmperf_snapshot_khz(void *dummy)
u64 aperf, aperf_delta;
u64 mperf, mperf_delta;
struct aperfmperf_sample *s = this_cpu_ptr(&samples);
- ktime_t now = ktime_get();
- s64 time_delta = ktime_ms_delta(now, s->time);
unsigned long flags;
local_irq_save(flags);
@@ -57,38 +57,68 @@ static void aperfmperf_snapshot_khz(void *dummy)
if (mperf_delta == 0)
return;
- s->time = now;
+ s->time = ktime_get();
s->aperf = aperf;
s->mperf = mperf;
-
- /* If the previous iteration was too long ago, discard it. */
- if (time_delta > APERFMPERF_STALE_THRESHOLD_MS)
- s->khz = 0;
- else
- s->khz = div64_u64((cpu_khz * aperf_delta), mperf_delta);
+ s->khz = div64_u64((cpu_khz * aperf_delta), mperf_delta);
}
-unsigned int arch_freq_get_on_cpu(int cpu)
+static bool aperfmperf_snapshot_cpu(int cpu, ktime_t now, bool wait)
{
- s64 time_delta;
- unsigned int khz;
+ s64 time_delta = ktime_ms_delta(now, per_cpu(samples.time, cpu));
+
+ /* Don't bother re-computing within the cache threshold time. */
+ if (time_delta < APERFMPERF_CACHE_THRESHOLD_MS)
+ return true;
+
+ smp_call_function_single(cpu, aperfmperf_snapshot_khz, NULL, wait);
+
+ /* Return false if the previous iteration was too long ago. */
+ return time_delta <= APERFMPERF_STALE_THRESHOLD_MS;
+}
+unsigned int aperfmperf_get_khz(int cpu)
+{
if (!cpu_khz)
return 0;
if (!static_cpu_has(X86_FEATURE_APERFMPERF))
return 0;
- /* Don't bother re-computing within the cache threshold time. */
- time_delta = ktime_ms_delta(ktime_get(), per_cpu(samples.time, cpu));
- khz = per_cpu(samples.khz, cpu);
- if (khz && time_delta < APERFMPERF_CACHE_THRESHOLD_MS)
- return khz;
+ aperfmperf_snapshot_cpu(cpu, ktime_get(), true);
+ return per_cpu(samples.khz, cpu);
+}
- smp_call_function_single(cpu, aperfmperf_snapshot_khz, NULL, 1);
- khz = per_cpu(samples.khz, cpu);
- if (khz)
- return khz;
+void arch_freq_prepare_all(void)
+{
+ ktime_t now = ktime_get();
+ bool wait = false;
+ int cpu;
+
+ if (!cpu_khz)
+ return;
+
+ if (!static_cpu_has(X86_FEATURE_APERFMPERF))
+ return;
+
+ for_each_online_cpu(cpu)
+ if (!aperfmperf_snapshot_cpu(cpu, now, false))
+ wait = true;
+
+ if (wait)
+ msleep(APERFMPERF_REFRESH_DELAY_MS);
+}
+
+unsigned int arch_freq_get_on_cpu(int cpu)
+{
+ if (!cpu_khz)
+ return 0;
+
+ if (!static_cpu_has(X86_FEATURE_APERFMPERF))
+ return 0;
+
+ if (aperfmperf_snapshot_cpu(cpu, ktime_get(), true))
+ return per_cpu(samples.khz, cpu);
msleep(APERFMPERF_REFRESH_DELAY_MS);
smp_call_function_single(cpu, aperfmperf_snapshot_khz, NULL, 1);
diff --git a/arch/x86/kernel/cpu/cpu.h b/arch/x86/kernel/cpu/cpu.h
index f52a370b6c00..e806b11a99af 100644
--- a/arch/x86/kernel/cpu/cpu.h
+++ b/arch/x86/kernel/cpu/cpu.h
@@ -47,4 +47,7 @@ extern const struct cpu_dev *const __x86_cpu_dev_start[],
extern void get_cpu_cap(struct cpuinfo_x86 *c);
extern void cpu_detect_cache_sizes(struct cpuinfo_x86 *c);
+
+unsigned int aperfmperf_get_khz(int cpu);
+
#endif /* ARCH_X86_CPU_H */
diff --git a/arch/x86/kernel/cpu/proc.c b/arch/x86/kernel/cpu/proc.c
index 6b7e17bf0b71..e7ecedafa1c8 100644
--- a/arch/x86/kernel/cpu/proc.c
+++ b/arch/x86/kernel/cpu/proc.c
@@ -5,6 +5,8 @@
#include <linux/seq_file.h>
#include <linux/cpufreq.h>
+#include "cpu.h"
+
/*
* Get CPU information for use by the procfs.
*/
@@ -78,9 +80,11 @@ static int show_cpuinfo(struct seq_file *m, void *v)
seq_printf(m, "microcode\t: 0x%x\n", c->microcode);
if (cpu_has(c, X86_FEATURE_TSC)) {
- unsigned int freq = cpufreq_quick_get(cpu);
+ unsigned int freq = aperfmperf_get_khz(cpu);
if (!freq)
+ freq = cpufreq_quick_get(cpu);
+ if (!freq)
freq = cpu_khz;
seq_printf(m, "cpu MHz\t\t: %u.%03u\n",
freq / 1000, (freq % 1000));
diff --git a/fs/proc/cpuinfo.c b/fs/proc/cpuinfo.c
index e0f867cd8553..96f1087e372c 100644
--- a/fs/proc/cpuinfo.c
+++ b/fs/proc/cpuinfo.c
@@ -1,12 +1,18 @@
// SPDX-License-Identifier: GPL-2.0
+#include <linux/cpufreq.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
+__weak void arch_freq_prepare_all(void)
+{
+}
+
extern const struct seq_operations cpuinfo_op;
static int cpuinfo_open(struct inode *inode, struct file *file)
{
+ arch_freq_prepare_all();
return seq_open(file, &cpuinfo_op);
}
diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index 537ff842ff73..cbf85c4c745f 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -917,6 +917,7 @@ static inline bool policy_has_boost_freq(struct cpufreq_policy *policy)
}
#endif
+extern void arch_freq_prepare_all(void);
extern unsigned int arch_freq_get_on_cpu(int cpu);
/* the following are really really optional */