topology.c

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/*
 *  (C) 2010,2011       Thomas Renninger <[email protected]>, Novell Inc.
 *
 *  Licensed under the terms of the GNU GPL License version 2.
 *
 * ToDo: Needs to be done more properly for AMD/Intel specifics
 */

/* Helper struct for qsort, must be in sync with cpupower_topology.cpu_info */
/* Be careful: Need to pass unsigned to the sort, so that offlined cores are
   in the end, but double check for -1 for offlined cpus at other places */

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>

#include <helpers/helpers.h>
#include <helpers/sysfs.h>

/* returns -1 on failure, 0 on success */
int sysfs_topology_read_file(unsigned int cpu, const char *fname)
{
    unsigned long value;
    char linebuf[MAX_LINE_LEN];
    char *endp;
    char path[SYSFS_PATH_MAX];

    snprintf(path, sizeof(path), PATH_TO_CPU "cpu%u/topology/%s",
             cpu, fname);
    if (sysfs_read_file(path, linebuf, MAX_LINE_LEN) == 0)
        return -1;
    value = strtoul(linebuf, &endp, 0);
    if (endp == linebuf || errno == ERANGE)
        return -1;
    return value;
}

struct cpuid_core_info {
    unsigned int pkg;
    unsigned int thread;
    unsigned int cpu;
    /* flags */
    unsigned int is_online:1;
};

static int __compare(const void *t1, const void *t2)
{
    struct cpuid_core_info *top1 = (struct cpuid_core_info *)t1;
    struct cpuid_core_info *top2 = (struct cpuid_core_info *)t2;
    if (top1->pkg < top2->pkg)
        return -1;
    else if (top1->pkg > top2->pkg)
        return 1;
    else if (top1->thread < top2->thread)
        return -1;
    else if (top1->thread > top2->thread)
        return 1;
    else if (top1->cpu < top2->cpu)
        return -1;
    else if (top1->cpu > top2->cpu)
        return 1;
    else
        return 0;
}

/*
 * Returns amount of cpus, negative on error, cpu_top must be
 * passed to cpu_topology_release to free resources
 *
 * Array is sorted after ->pkg, ->core, then ->cpu
 */
int get_cpu_topology(struct cpupower_topology *cpu_top)
{
    int cpu, cpus = sysconf(_SC_NPROCESSORS_CONF);

    cpu_top->core_info = malloc(sizeof(struct cpupower_topology) * cpus);
    if (cpu_top->core_info == NULL)
        return -ENOMEM;
    cpu_top->pkgs = cpu_top->cores = 0;
    for (cpu = 0; cpu < cpus; cpu++) {
        cpu_top->core_info[cpu].cpu = cpu;
        cpu_top->core_info[cpu].is_online = sysfs_is_cpu_online(cpu);
        cpu_top->core_info[cpu].pkg =
            sysfs_topology_read_file(cpu, "physical_package_id");
        if ((int)cpu_top->core_info[cpu].pkg != -1 &&
            cpu_top->core_info[cpu].pkg > cpu_top->pkgs)
            cpu_top->pkgs = cpu_top->core_info[cpu].pkg;
        cpu_top->core_info[cpu].core =
            sysfs_topology_read_file(cpu, "core_id");
    }
    cpu_top->pkgs++;

    qsort(cpu_top->core_info, cpus, sizeof(struct cpuid_core_info),
          __compare);

    /* Intel's cores count is not consecutively numbered, there may
     * be a core_id of 3, but none of 2. Assume there always is 0
     * Get amount of cores by counting duplicates in a package
    for (cpu = 0; cpu_top->core_info[cpu].pkg = 0 && cpu < cpus; cpu++) {
        if (cpu_top->core_info[cpu].core == 0)
    cpu_top->cores++;
    */
    return cpus;
}

void cpu_topology_release(struct cpupower_topology cpu_top)
{
    free(cpu_top.core_info);
}