Commit fb4c77c2 authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

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



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: default avatar"Rafael J. Wysocki" <rafael@kernel.org>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Tested-by: default avatarDoug Smythies <dsmythies@telus.net>
Link: https://lore.kernel.org/r/87pml5180p.ffs@tglx
parent f3eca381

arch/x86/kernel/cpu/aperfmperf.c

+7 −3
Original line number Diff line number Diff line
@@ -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)

arch/x86/kernel/cpu/proc.c

+1 −6
Original line number Diff line number Diff line
@@ -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 */