Get cpu usage in iOS
To obtain the cpu usage in Objective-C you must call a C function.
Fortunately, Objective-C gets full support for C and C++ so you can write a C function named cpu_usage and use it writing cpu_usage().
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; basic_info = (task_basic_info_t)tinfo; 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 < 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->system_time.microseconds + basic_info_th->system_time.microseconds; tot_cpu = tot_cpu + basic_info_th->cpu_usage / (float)TH_USAGE_SCALE * 100.0; } } kr = vm_deallocate(mach_task_self(), (vm_offset_t)thread_list, thread_count * sizeof(thread_t)); assert(kr == KERN_SUCCESS); return tot_cpu; }
The cpu_usage function returns the cpu usage like a float number.
Well, if you want to schedule the cpu_usage C function to monitoring the cpu, you can use a NSTimer that calls a Objective-C method that calls the C function.
Basically, create a Objective-C method like below
-(void)cpu_usage //it is a Objective-C method { float averageCpuUsage = cpu_usage(); //it calls the cpu_usage() C function NSLog(@"CPU usage is %f", averageCpuUsage); }
and use a NSTimer (named cpuMonitor, it's a private variable define in the interface class) to schedule it
cpuMonitor = [NSTimer scheduledTimerWithTimeInterval:5 target:self selector:@selector(cpu_usage) userInfo:nil repeats:YES]; //it calls the cpu_usage Objective-C method
That's all.