op_cpufreq.c

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#include <stdio.h>
#include <stdlib.h>

#include "op_fileio.h"

/*
 * Use frequency information from /proc/cpuinfo. This should be available in most case.
 * However, this number is the current cpu frequency which could be in the idle state.
 * We should actually report the max frequency because the cpu should switch into the
 * highest power state when running.
 */
static double op_cpu_freq_cpuinfo(void)
{
    double fval = 0.0;
    unsigned long uval;
    char * line = NULL;

    FILE * fp = op_try_open_file("/proc/cpuinfo", "r");
    if (!fp)
        return 0.0;

    while (1) {
        line = op_get_line(fp);

        if (!line)
            break;

        if (line[0] == '\0') {
            free(line);
            continue;
        }

        /* x86/parisc/ia64/x86_64 */
        if (sscanf(line, "cpu MHz : %lf", &fval) == 1)
            break;
        /* ppc/ppc64 */
        if (sscanf(line, "clock : %lfMHz", &fval) == 1)
            break;
        /* alpha */
        if (sscanf(line, "cycle frequency [Hz] : %lu", &uval) == 1) {
            fval = uval / 1E6;
            break;
        }
        /* sparc64 if CONFIG_SMP only */
        if (sscanf(line, "Cpu0ClkTck : %lx", &uval) == 1) {
            fval = uval / 1E6;
            break;
        }
        /* mips including loongson2 */
        if (sscanf(line, "BogoMIPS      : %lu", &uval) == 1) {
            fval = uval * 3 / 2;
            break;
        }
        /* s390 doesn't provide cpu freq, checked up to 2.6-test4 */

        free(line);
    }

    if (line)
        free(line);
    op_close_file(fp);

    return fval;
}


/*
 * Use frequency information from /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq
 * This number is the maximum cpu frequency of the processor.
 */
static double op_cpu_freq_sys_devices(void)
{
    double fval = 0.0;
    char * line = NULL;

    FILE * fp = op_try_open_file("/sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq", "r");
    if (!fp)
        return 0.0;

    while (1) {
        line = op_get_line(fp);

        if (!line)
            break;

        if (line[0] == '\0') {
            free(line);
            continue;
        }

        if (sscanf(line, "%lf", &fval) == 1)
            break;

        free(line);
    }

    if (line)
        free(line);
    op_close_file(fp);

    return fval;
}


double op_cpu_frequency(void)
{
    /*
     * Typically, system changes the frequency scaling of the cpus
     * based on the workload.  /proc/cpuinfo reports the current
     * frequency value which might not be at the maximum at the time
     * of query.  Since cpu switch into running state with max frequency
     * when under workload, we should make sure to report the max frequency
     * value acquiring from /sys/devices when available.
     */

    double freq = op_cpu_freq_sys_devices();
    if (freq == 0) {
        freq = op_cpu_freq_cpuinfo();
    }
    return freq;
}