最近在调研iOS中的OOM(Out-Of-Memory),iOS中存在一些机制,当系统的内存不够用时或者当前APP的使用内存超过了阈值,就会导致系统强杀当前APP,由于强杀当前APP的进程是系统做的事情,所以,当前APP是无法知道是什么时候被强杀的。而且,我们平常使用的通过监测signal信号量来获取Crash的工具也是无法获取OOM这类强杀的。在调研测试过程中,用到了计算当前APP占用内存的计算方法和CPU使用率的计算方法,在此记录一下。
获取当前APP占用系统内存的方法如下:
#import <mach/mach.h>
- (int64_t)memoryUsage {
int64_t memoryUsageInByte = 0;
task_vm_info_data_t vmInfo;
mach_msg_type_number_t count = TASK_VM_INFO_COUNT;
kern_return_t kernelReturn = task_info(mach_task_self(), TASK_VM_INFO, (task_info_t) &vmInfo, &count);
if(kernelReturn == KERN_SUCCESS) {
memoryUsageInByte = (int64_t) vmInfo.phys_footprint;
NSLog(@"APP占用内存: %lld字节(B)", memoryUsageInByte);
int64_t mb = memoryUsageInByte / 1024 / 1024;
NSLog(@"APP占用内存: %lld兆(MB)", mb);
} else {
NSLog(@"Error with task_info(): %s", mach_error_string(kernelReturn));
}
return memoryUsageInByte;
}
计算当前APP的CPU使用率的方法(数值与Instrument计算值接近):
- (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->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;
}