Question

How do I obtain CPU usage for an application? It’s definitely possible, because there are application in App store (Activity Monitor Touch) which can show it.

Answer 1

Update. This code is working for me:

Update 2. The thread_list was leaking, so added vm_deallocate

#import <mach/mach.h>
#import <assert.h>

float cpu_usage()
{
    kern_return_t kr;
    task_info_data_t tinfo;
    mach_msg_type_number_t task_info_count;

    task_info_count = TASK_INFO_MAX;
    kr = task_info(mach_task_self(), TASK_BASIC_INFO, (task_info_t)tinfo, &task_info_count);
    if (kr != KERN_SUCCESS) {
        return -1;
    }

    task_basic_info_t      basic_info;
    thread_array_t         thread_list;
    mach_msg_type_number_t thread_count;

    thread_info_data_t     thinfo;
    mach_msg_type_number_t thread_info_count;

    thread_basic_info_t basic_info_th;
    uint32_t stat_thread = 0; // Mach threads

    basic_info = (task_basic_info_t)tinfo;

    // get threads in the task
    kr = task_threads(mach_task_self(), &thread_list, &thread_count);
    if (kr != KERN_SUCCESS) {
        return -1;
    }
    if (thread_count > 0)
        stat_thread += thread_count;

    long tot_sec = 0;
    long tot_usec = 0;
    float tot_cpu = 0;
    int j;

    for (j = 0; j < (int)thread_count; j++)
    {
        thread_info_count = THREAD_INFO_MAX;
        kr = thread_info(thread_list[j], THREAD_BASIC_INFO,
                         (thread_info_t)thinfo, &thread_info_count);
        if (kr != KERN_SUCCESS) {
            return -1;
        }

        basic_info_th = (thread_basic_info_t)thinfo;

        if (!(basic_info_th->flags & TH_FLAGS_IDLE)) {
            tot_sec = tot_sec + basic_info_th->user_time.seconds + basic_info_th->system_time.seconds;
            tot_usec = tot_usec + basic_info_th->user_time.microseconds + basic_info_th->system_time.microseconds;
            tot_cpu = tot_cpu + basic_info_th->cpu_usage / (float)TH_USAGE_SCALE * 100.0;
        }

    } // for each thread

    kr = vm_deallocate(mach_task_self(), (vm_offset_t)thread_list, thread_count * sizeof(thread_t));
    assert(kr == KERN_SUCCESS);

    return tot_cpu;
}