怎么获取某个APP的CPU和内存占用

-(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 < 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;
}

} // 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;
}