Function cbm_detect_cgroup_mem

src/foundation/system_info.c:176–207

Effective memory limit from a cgroup file tree. See header for contract. */

/* Effective memory limit from a cgroup file tree. See header for contract. */
size_t cbm_detect_cgroup_mem(const char *cgroup_root) {
    char path[CBM_PATH_MAX];
    char buf[CBM_SZ_64];

    /* cgroup v2: "<root>/memory.max" — "max" or integer bytes. */
    snprintf(path, sizeof(path), "%s/memory.max", cgroup_root);
    if (read_small_file(path, buf, sizeof(buf)) > 0) {
        if (strncmp(buf, "max", 3) == 0) {
            return 0;
        }
        char *end = NULL;
        unsigned long long n = strtoull(buf, &end, CBM_DECIMAL_BASE);
        if (end == buf || n == 0) {
            return 0;
        }
        return (size_t)n;
    }

    /* cgroup v1: ".../memory/memory.limit_in_bytes". The sentinel for
     * "unlimited" is a very large value (~PAGE_COUNTER_MAX); treat anything
     * past half of ULLONG_MAX as effectively unlimited. */
    snprintf(path, sizeof(path), "%s/memory/memory.limit_in_bytes", cgroup_root);
    if (read_small_file(path, buf, sizeof(buf)) <= 0) {
        return 0;
    }
    char *end = NULL;
    unsigned long long n = strtoull(buf, &end, CBM_DECIMAL_BASE);
    if (end == buf || n == 0 || n >= (ULLONG_MAX / 2)) {
        return 0;
    }
    return (size_t)n;
}

static cbm_system_info_t detect_system_linux(void) {
    cbm_system_info_t info;