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supports/ticks: read cpufreq from sysfs/procfs #42

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Merged
minwooim merged 1 commit into from
Aug 14, 2025
Merged

supports/ticks: read cpufreq from sysfs/procfs #42

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53 changes: 53 additions & 0 deletions src/support/ticks.c
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,9 @@
#include <stdbool.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sched.h>
#include <unistd.h>

#include "vfn/support/align.h"
Expand All @@ -29,6 +32,53 @@

uint64_t __vfn_ticks_freq;

static uint64_t read_cpu_freq_from_sys(void)
{
uint64_t hz = 0;
char buf[256];
double mhz;
FILE *f;
int cpu;

cpu = sched_getcpu();
if (cpu < 0)
cpu = 0;

sprintf(buf, "/sys/devices/system/cpu/cpu%d/cpufreq/cpuinfo_max_freq", cpu);
f = fopen(buf, "r");
if (f) {
if (fgets(buf, sizeof(buf), f))
/* Convert KHz -> Hz */
hz = strtoull(buf, NULL, 10) * 1000;
fclose(f);
if (hz)
return ROUND(hz, TICKS_PER_10MHZ);
}

/* Second chance from procfs */
f = fopen("/proc/cpuinfo", "r");
if (f) {
int current_cpu = 0;
int proc_cpu;

while (fgets(buf, sizeof(buf), f)) {
if (sscanf(buf, "processor : %d", &proc_cpu) == 1)
current_cpu = proc_cpu;
else if (current_cpu == cpu) {
if (sscanf(buf, "cpu MHz : %lf", &mhz) == 1) {
hz = (uint64_t)(mhz * 1000000);
break;
}
}
}
fclose(f);
if (hz)
return ROUND(hz, TICKS_PER_10MHZ);
}

return 0;
}

static uint64_t measure_ticks_freq(void)
{
struct timemono t_start, t_end;
Expand Down Expand Up @@ -78,6 +128,9 @@ static void __attribute__((constructor)) init_ticks_freq(void)
uint64_t freq;

freq = get_ticks_freq_arch();
if (!freq)
freq = read_cpu_freq_from_sys();

if (!freq)
freq = measure_ticks_freq();

Expand Down
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