为了提高应用的体验，我们需要对程序作出优化。难点不在如何做优化，而在找出优化的点。
优化常见的手段就是：
1 异步读写：图片，数据库，沙盒文件，plist等
2 异步处理数据：后台解析数据，异步计算UI高度，异步处理图片如圆角
3 缓存：保存处理后的数据（UI高度，lable高度），图片等
找出需要优化的地方，才是本文重点.

监控窗口，可移动位置

我们做一个浮窗，实时监控每一步操作的性能表现， 对卡顿点做记录并保存文件。

计算内存

#include <mach/mach.h>
#include <mach/task_info.h>
#include <sys/types.h>
#include <sys/sysctl.h>
- (vm_size_t)getUsedMemory
{
    struct mach_task_basic_info info;
    mach_msg_type_number_t size = MACH_TASK_BASIC_INFO_COUNT;
    kern_return_t kerr = task_info(mach_task_self(), MACH_TASK_BASIC_INFO, (task_info_t)&info, &size);
    return (kerr == KERN_SUCCESS) ? info.resident_size : 0; // size in bytes
}

计算CPU

- (float)getUsedCPU
{
    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;
}

计算FPS

CADisplayLink *_fpsLink;
 NSUInteger _count;
 NSTimeInterval _lastTime;
 float _fpsValue;

- (void)startFpsDisplayLink
{
    if (!_fpsLink) {
        _fpsLink = [CADisplayLink displayLinkWithTarget:self selector:@selector(tick:)];
        [_fpsLink addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSRunLoopCommonModes];
    }
}

- (void)stopFpsDisplayLink
{
    if(_fpsLink){
        [_fpsLink invalidate];
        _fpsLink = nil;
    }
}

- (void)tick:(CADisplayLink *)displayLink
{
    if (0 == _lastTime) {
        _lastTime = displayLink.timestamp;
        return;
    }
    
    _count ++;
    NSTimeInterval delta = displayLink.timestamp - _lastTime;
    if (delta < 1) {
        return;
    }
    _fpsValue = _count / delta;
    _lastTime = displayLink.timestamp;
    _count = 0;
}

记录卡顿点，打印卡顿堆栈

可查看卡顿代码

源码下载

https://github.com/FSilver/FWMonitor

FWMonitorView *view = [FWMonitorView monitor];
[[UIApplication sharedApplication].keyWindow addSubView:view];

只需两行代码，即可完成所有监控指标