日常app发现性能问题往往需要通过用户反馈，再通过分析代码进行优化。为了更高效的定位问题，需要收集app相关的性能指标，例如CPU、RAM、FPS、启动时长、网络等。下面通过一些系统api来统计这些指标，了解这些指标的具体含义，通过对比，获取的指标数据与Xcode基本是一致的。
CPU
1、CPU Core Count
首先是获取系统的内核数，Xcode上显示的CPU最大占用率，往往在不同设备也不同，这个和内核数有关，例如调试设备iphone11（6核），显示最大占用为600%，设备ipad mini2（双核），显示最大占用为200%，所以多线程场景下可能超过100%的情况。
+ (NSUInteger)sysCoresCount {
return [NSProcessInfo processInfo].activeProcessorCount;}
2、App CPU Usage
获取应用的CPU占用，app作为一个进程在系统中运行，运行进程又包含多个线程，线程是系统调度和分配的基本单位，如果可以获取到每一条线程的CPU占用就可以知道整个进程的数据，Xcode也提供当前应用每个线程的CPU图表数据，所有线程的CPU累加就得到应用的CPU占用。
通过task_threads(mach_task_self(), &thread_list, &thread_count)获取到thread_list，返回kern_return_t类型，其实是int类型，返回0表示成功，task可以理解为多个线程运行环境的抽象。mach_task_self()入参表示当前应用，遍历所有线程，thread_info(thread_list[j], THREAD_BASIC_INFO,(thread_info_t)thinfo, &thread_info_count)获取每个线程信息，thread_basic_info_t类型是一个结构体，包含的cpu_usage就是线程的CPU占用。
struct thread_basic_info {
time_value_t user_time; /* user run time */
time_value_t system_time; /* system run time */
integer_t cpu_usage; /* scaled cpu usage percentage */
policy_t policy; /* scheduling policy in effect */
integer_t run_state; /* run state (see below) */
integer_t flags; /* various flags (see below) */
integer_t suspend_count; /* suspend count for thread */
integer_t sleep_time; /* number of seconds that thread
* has been sleeping */
};
+ (CGFloat)appCpuUsage {
kern_return_t kr;
task_info_data_t tinfo;
mach_msg_type_number_t task_info_count;
task_info_count = TASK_INFO_MAX;
// task 线程执行环境的抽象
kr = task_info(mach_task_self(), MACH_TASK_BASIC_INFO, (task_info_t)tinfo, &task_info_count);
if (kr != KERN_SUCCESS) {
return -1.f;
}
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;
// get threads in the task
kr = task_threads(mach_task_self(), &thread_list, &thread_count);
if (kr != KERN_SUCCESS) {
return -1.f;
}
long total_time = 0;
long total_userTime = 0;
CGFloat total_cpu = 0;
// for each thread
for (int i = 0; i < (int)thread_count; i++) { thread_info_count = THREAD_INFO_MAX;
kr = thread_info(thread_list[i], 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)) {
total_time = total_time + basic_info_th->user_time.seconds + basic_info_th->system_time.seconds;
total_userTime = total_userTime + basic_info_th->user_time.microseconds + basic_info_th->system_time.microseconds;
total_cpu = total_cpu + basic_info_th->cpu_usage / (float)TH_USAGE_SCALE;
}
}
kr = vm_deallocate(mach_task_self(), (vm_offset_t)thread_list, thread_count * sizeof(thread_t));
assert(kr == KERN_SUCCESS);
return total_cpu;
}
3、System CPU Usage
分别计算CPU各个状态下的差值，kernel CPU的四种状态，user、nice、system、idle，idle是空闲状态不计入Usage。
+ (CGFloat)sysCpuUsage {
kern_return_t kr;
mach_msg_type_number_t count;
static host_cpu_load_info_data_t host_cpu_load_info = {0, 0, 0, 0};
host_cpu_load_info_data_t info;
count = HOST_CPU_LOAD_INFO_COUNT;
kr = host_statistics64(mach_host_self(), HOST_CPU_LOAD_INFO, (host_info64_t)&info, &count);
if (kr != KERN_SUCCESS) {
return -1.f;
}
natural_t user = info.cpu_ticks[CPU_STATE_USER] - host_cpu_load_info.cpu_ticks[CPU_STATE_USER];
natural_t nice = info.cpu_ticks[CPU_STATE_NICE] - host_cpu_load_info.cpu_ticks[CPU_STATE_NICE]; // 进程的执行优先级
natural_t system = info.cpu_ticks[CPU_STATE_SYSTEM] - host_cpu_load_info.cpu_ticks[CPU_STATE_SYSTEM];
natural_t idle = info.cpu_ticks[CPU_STATE_IDLE] - host_cpu_load_info.cpu_ticks[CPU_STATE_IDLE]; // CPU空闲状态
natural_t total = user + nice + system + idle;
host_cpu_load_info = info;
return (user + nice + system) * 100.0 / total;
}
RAM
1、App Memory Usage
+ (NSUInteger)appMemoryUsage {
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) {
return vmInfo.phys_footprint;
} else {
return -1;
}
}
2、System Memory Usage
系统的内存主要由这几个部分组成：
Wired memory：
Active memory：当前系统正在使用并且最近在使用的内存。
Inactive memory：当前没有在使用但最近在使用的内存，例如，某个app当前退出，之前使用的那部分内存标记为Inactive memory，当系统内存告急时可以被其他应用使用，如果在被其他应用使用之前再次打开app，将非活跃内存转化成活跃内存，开启速度则更快。
Free memory：空闲的那部分内存，未被使用的。
从Apple的文档Memory Usage Performance Guidelines可以找到相关内容。
需要注意的是vm_statistics64_data_t vmstat使用64位防止数据溢出，
+ (NSUInteger)sysMemoryUsage {
vm_size_t pagesize = 4096;
mach_msg_type_number_t count = HOST_VM_INFO64_COUNT;
vm_statistics64_data_t vmstat;
if (host_statistics64(mach_host_self(), HOST_VM_INFO64, (host_info64_t)&vmstat, &count) != KERN_SUCCESS) {
return 0;
}
long long wireMemory = vmstat.wire_count * pagesize; // 当前应用使用的基础Memory
long long activeMemory = vmstat.active_count * pagesize; // 当前active状态的Memory
long long inactiveMemory = vmstat.inactive_count * pagesize; // 当前inactive状态的Memory
return wireMemory + activeMemory + inactiveMemory;
}
3、Total Physical Memory
+ (NSUInteger)totalPhysicalMemory {
return [NSProcessInfo processInfo].physicalMemory;;
}
