49

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.

4
  • 1
    You need to find out why task_info() is failing and that will help you move on. See the answer to this SO question: stackoverflow.com/questions/5182924/…. I think it's cos you haven't initialised port; use task_info_self() instead of port.
    – trojanfoe
    Commented Nov 22, 2011 at 11:25
  • 1
    Wow, thanks for that! Now this code seems to be working. The only correction that we need mach_task_self(), not task_info_self().
    – ivanzoid
    Commented Nov 22, 2011 at 12:44
  • 1
    Please write it as an answer. And wait some time, if these is no other good answer, accept it.
    – Tinyfool
    Commented Dec 3, 2011 at 14:33
  • @jww Already monitor cpu usage successfully by your way; But can you help answer my related questions? stackoverflow.com/questions/47071265/…
    – Paradise
    Commented Nov 2, 2017 at 9:12

3 Answers 3

83

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;
}
17
  • 1
    Does this give CPU usage for the app or overall CPU usage? Commented Aug 7, 2012 at 6:08
  • 1
    Thanks for your quick reply. Is there any way I can get the overall CPU usage? Commented Aug 7, 2012 at 8:10
  • i use this code to calculate the cpu usage but it always return 0 from this function.. Please help
    – Saiful
    Commented Sep 19, 2012 at 6:50
  • 4
    is there a way to get cpu usage by process id?
    – Rukshan
    Commented Oct 15, 2012 at 6:22
  • 2
    In the line where the microseconds are added up, the system time is added twice. This should probably be user time + system time instead.
    – George
    Commented Aug 26, 2015 at 16:46
11

For Swift 3:

fileprivate func cpuUsage() -> Double {
    var kr: kern_return_t
    var task_info_count: mach_msg_type_number_t

    task_info_count = mach_msg_type_number_t(TASK_INFO_MAX)
    var tinfo = [integer_t](repeating: 0, count: Int(task_info_count))

    kr = task_info(mach_task_self_, task_flavor_t(TASK_BASIC_INFO), &tinfo, &task_info_count)
    if kr != KERN_SUCCESS {
        return -1
    }

    var thread_list: thread_act_array_t? = UnsafeMutablePointer(mutating: [thread_act_t]())
    var thread_count: mach_msg_type_number_t = 0
    defer {
        if let thread_list = thread_list {
            vm_deallocate(mach_task_self_, vm_address_t(UnsafePointer(thread_list).pointee), vm_size_t(thread_count))
        }
    }

    kr = task_threads(mach_task_self_, &thread_list, &thread_count)

    if kr != KERN_SUCCESS {
        return -1
    }

    var tot_cpu: Double = 0

    if let thread_list = thread_list {

        for j in 0 ..< Int(thread_count) {
            var thread_info_count = mach_msg_type_number_t(THREAD_INFO_MAX)
            var thinfo = [integer_t](repeating: 0, count: Int(thread_info_count))
            kr = thread_info(thread_list[j], thread_flavor_t(THREAD_BASIC_INFO),
                             &thinfo, &thread_info_count)
            if kr != KERN_SUCCESS {
                return -1
            }

            let threadBasicInfo = convertThreadInfoToThreadBasicInfo(thinfo)

            if threadBasicInfo.flags != TH_FLAGS_IDLE {
                tot_cpu += (Double(threadBasicInfo.cpu_usage) / Double(TH_USAGE_SCALE)) * 100.0
            }
        } // for each thread
    }

    return tot_cpu
}

fileprivate func convertThreadInfoToThreadBasicInfo(_ threadInfo: [integer_t]) -> thread_basic_info {
    var result = thread_basic_info()

    result.user_time = time_value_t(seconds: threadInfo[0], microseconds: threadInfo[1])
    result.system_time = time_value_t(seconds: threadInfo[2], microseconds: threadInfo[3])
    result.cpu_usage = threadInfo[4]
    result.policy = threadInfo[5]
    result.run_state = threadInfo[6]
    result.flags = threadInfo[7]
    result.suspend_count = threadInfo[8]
    result.sleep_time = threadInfo[9]

    return result
}
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  • 2
    I have a question: Is the calculation of the CPU usage of my application, or is it the calculation of the CPU use of the iOS?
    – Markus
    Commented Nov 23, 2017 at 9:58
  • 3
    Hi Markus, this function return the CPU usage of your application.
    – Lionking
    Commented Nov 27, 2017 at 2:04
  • 2
    I think the vm_deallocate is incorrect. Certainly in Swift 4 the correct way to call it would be vm_deallocate(mach_task_self_, vm_address_t(bitPattern: thread_list), vm_size_t(Int(thread_count) * MemoryLayout<thread_t>.stride) ) Accessing thread_list.pointee would return the first value of thread_list, not the address of the array itself.
    – kuwerty
    Commented May 11, 2018 at 8:57
  • thanks @kuwerty! otherwise it was constantly leaking. Commented Apr 13, 2022 at 12:48
  • 1
    @GregOriol sure, here it is: gist.github.com/smocer/2813ae815c70aa1ee165ecf89515804a
    – smocer
    Commented Jan 24 at 9:13
0

Try this:

- (NSString *)cpuUsage
{
   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 @"NA";
   }

   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 @"NA";
   }
   if (thread_count > 0)
    stat_thread += thread_count;

   long tot_idle = 0;
   long tot_user = 0;
   long tot_kernel = 0;
   int j;

   for (j = 0; j < 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 nil;
      }

      basic_info_th = (thread_basic_info_t)thinfo;

      if (basic_info_th->flags & TH_FLAGS_IDLE)
      {
          //This is idle
          tot_idle = tot_idle + basic_info_th->user_time.microseconds + basic_info_th->system_time.microseconds;
      } else {
          //This is user
          tot_user = tot_user + basic_info_th->user_time.microseconds;

          //This is kernel
          tot_kernel = tot_kernel + basic_info_th->system_time.microseconds;
      }

  } // for each thread

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

  long tot_cpu = tot_idle + tot_user + tot_kernel

  return [NSString stringWithFormat:@"Idle: %.2f, User: %.2f, Kernel: %.2f", tot_idle/tot_cpu, tot_user/tot_cpu, tot_kernel/tot_cpu];
}

However, that method calculates the percentages based on the starting point of each process. If you are looking for the more traditional way of calculating these numbers, see Petesh's answer.

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