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x86/aperfmperf: Integrate the fallback code from show_cpuinfo()

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Due to the avoidance of IPIs to idle CPUs arch_freq_get_on_cpu() can return
0 when the last sample was too long ago.

show_cpuinfo() has a fallback to cpufreq_quick_get() and if that fails to
return cpu_khz, but the readout code for the per CPU scaling frequency in
sysfs does not.

Move that fallback into arch_freq_get_on_cpu() so the behaviour is the same
when reading /proc/cpuinfo and /sys/..../cur_scaling_freq.

Suggested-by: "Rafael J. Wysocki" <rafael@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Doug Smythies <dsmythies@telus.net>
Link: https://lore.kernel.org/r/87pml5180p.ffs@tglx
This commit is contained in:
Thomas Gleixner 2022-04-25 17:45:42 +02:00
parent f3eca381bd
commit fb4c77c21a
2 changed files with 8 additions and 9 deletions
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10
arch/x86/kernel/cpu/aperfmperf.c
View file

@ -405,12 +405,12 @@ void arch_scale_freq_tick(void)
unsigned int arch_freq_get_on_cpu(int cpu)
{
struct aperfmperf *s = per_cpu_ptr(&cpu_samples, cpu);
unsigned int seq, freq;
unsigned long last;
unsigned int seq;
u64 acnt, mcnt;
if (!cpu_feature_enabled(X86_FEATURE_APERFMPERF))
return 0;
goto fallback;
do {
seq = raw_read_seqcount_begin(&s->seq);
@ -424,9 +424,13 @@ unsigned int arch_freq_get_on_cpu(int cpu)
* which covers idle and NOHZ full CPUs.
*/
if (!mcnt || (jiffies - last) > MAX_SAMPLE_AGE)
return 0;
goto fallback;
return div64_u64((cpu_khz * acnt), mcnt);
fallback:
freq = cpufreq_quick_get(cpu);
return freq ? freq : cpu_khz;
}
static int __init bp_init_aperfmperf(void)

7
arch/x86/kernel/cpu/proc.c
View file

@ -86,12 +86,7 @@ static int show_cpuinfo(struct seq_file *m, void *v)
if (cpu_has(c, X86_FEATURE_TSC)) {
unsigned int freq = arch_freq_get_on_cpu(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));
seq_printf(m, "cpu MHz\t\t: %u.%03u\n", freq / 1000, (freq % 1000));
}
/* Cache size */