前言
本文的demo代码也会更新到github上。
做这个demo思路来源于微信team的：微信iOS卡顿监控系统。
主要思路:通过监测Runloop的kCFRunLoopAfterWaiting，用一个子线程去检查，一次循环是否时间太长。
其中主要涉及到了runloop的原理。关于整个原理：深入理解RunLoop讲解的比较仔细。
以下就是runloop大概的运行方式：
/// 1. 通知Observers，即将进入RunLoop
/// 此处有Observer会创建AutoreleasePool: _objc_autoreleasePoolPush();
__CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__(kCFRunLoopEntry);
do {
/// 2. 通知 Observers: 即将触发 Timer 回调。
__CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__(kCFRunLoopBeforeTimers);
/// 3. 通知 Observers: 即将触发 Source (非基于port的,Source0) 回调。
__CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__(kCFRunLoopBeforeSources);
__CFRUNLOOP_IS_CALLING_OUT_TO_A_BLOCK__(block);
/// 4. 触发 Source0 (非基于port的) 回调。
__CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__(source0);
/// 5. GCD处理main block
__CFRUNLOOP_IS_CALLING_OUT_TO_A_BLOCK__(block);
/// 6. 通知Observers，即将进入休眠
/// 此处有Observer释放并新建AutoreleasePool: _objc_autoreleasePoolPop(); _objc_autoreleasePoolPush();
__CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__(kCFRunLoopBeforeWaiting);
/// 7. sleep to wait msg.
mach_msg() -> mach_msg_trap();
/// 8. 通知Observers，线程被唤醒
__CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__(kCFRunLoopAfterWaiting);
/// 9. 如果是被Timer唤醒的，回调Timer
__CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__(timer);
/// 9. 如果是被dispatch唤醒的，执行所有调用 dispatch_async 等方法放入main queue 的 block
__CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__(dispatched_block);
/// 9. 如果如果Runloop是被 Source1 (基于port的) 的事件唤醒了，处理这个事件
__CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__(source1);
} while (...);
/// 10. 通知Observers，即将退出RunLoop
/// 此处有Observer释放AutoreleasePool: _objc_autoreleasePoolPop();
__CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__(kCFRunLoopExit);
}
其中UI主要集中在__CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__(source0);
和__CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__(source1);之前。
获取kCFRunLoopBeforeSources到kCFRunLoopBeforeWaiting再到kCFRunLoopAfterWaiting的状态就可以知道是否有卡顿的情况。
NSTimer的实现
具体代码如下：
//
// MonitorController.h
// RunloopMonitorDemo
//
// Created by game3108 on 16/4/13.
// Copyright © 2016年 game3108. All rights reserved.
//
#import <Foundation/Foundation.h>
@interface MonitorController : NSObject
+ (instancetype) sharedInstance;
- (void) startMonitor;
- (void) endMonitor;
- (void) printLogTrace;
@end
//
// MonitorController.m
// RunloopMonitorDemo
//
// Created by game3108 on 16/4/13.
// Copyright © 2016年 game3108. All rights reserved.
//
#import "MonitorController.h"
#include <libkern/OSAtomic.h>
#include <execinfo.h>
@interface MonitorController(){
CFRunLoopObserverRef _observer;
double _lastRecordTime;
NSMutableArray *_backtrace;
}
@end
@implementation MonitorController
static double _waitStartTime;
+ (instancetype) sharedInstance{
static dispatch_once_t once;
static id sharedInstance;
dispatch_once(&once, ^{
sharedInstance = [[self alloc] init];
});
return sharedInstance;
}
- (void) startMonitor{
[self addMainThreadObserver];
[self addSecondaryThreadAndObserver];
}
- (void) endMonitor{
if (!_observer) {
return;
}
CFRunLoopRemoveObserver(CFRunLoopGetMain(), _observer, kCFRunLoopCommonModes);
CFRelease(_observer);
_observer = NULL;
}
#pragma mark printLogTrace
- (void)printLogTrace{
NSLog(@"====================堆栈\n %@ \n",_backtrace);
}
#pragma mark addMainThreadObserver
- (void) addMainThreadObserver {
dispatch_async(dispatch_get_main_queue(), ^{
//建立自动释放池
@autoreleasepool {
//获得当前thread的Run loop
NSRunLoop *myRunLoop = [NSRunLoop currentRunLoop];
//设置Run loop observer的运行环境
CFRunLoopObserverContext context = {0, (__bridge void *)(self), NULL, NULL, NULL};
//创建Run loop observer对象
//第一个参数用于分配observer对象的内存
//第二个参数用以设置observer所要关注的事件，详见回调函数myRunLoopObserver中注释
//第三个参数用于标识该observer是在第一次进入run loop时执行还是每次进入run loop处理时均执行
//第四个参数用于设置该observer的优先级
//第五个参数用于设置该observer的回调函数
//第六个参数用于设置该observer的运行环境
_observer = CFRunLoopObserverCreate(kCFAllocatorDefault, kCFRunLoopAllActivities, YES, 0, &myRunLoopObserver, &context);
if (_observer) {
//将Cocoa的NSRunLoop类型转换成Core Foundation的CFRunLoopRef类型
CFRunLoopRef cfRunLoop = [myRunLoop getCFRunLoop];
//将新建的observer加入到当前thread的run loop
CFRunLoopAddObserver(cfRunLoop, _observer, kCFRunLoopDefaultMode);
}
}
});
}
void myRunLoopObserver(CFRunLoopObserverRef observer, CFRunLoopActivity activity, void *info) {
switch (activity) {
//The entrance of the run loop, before entering the event processing loop.
//This activity occurs once for each call to CFRunLoopRun and CFRunLoopRunInMode
case kCFRunLoopEntry:
NSLog(@"run loop entry");
break;
//Inside the event processing loop before any timers are processed
case kCFRunLoopBeforeTimers:
NSLog(@"run loop before timers");
break;
//Inside the event processing loop before any sources are processed
case kCFRunLoopBeforeSources:
NSLog(@"run loop before sources");
break;
//Inside the event processing loop before the run loop sleeps, waiting for a source or timer to fire.
//This activity does not occur if CFRunLoopRunInMode is called with a timeout of 0 seconds.
//It also does not occur in a particular iteration of the event processing loop if a version 0 source fires
case kCFRunLoopBeforeWaiting:{
_waitStartTime = 0;
NSLog(@"run loop before waiting");
break;
}
//Inside the event processing loop after the run loop wakes up, but before processing the event that woke it up.
//This activity occurs only if the run loop did in fact go to sleep during the current loop
case kCFRunLoopAfterWaiting:{
_waitStartTime = [[NSDate date] timeIntervalSince1970];
NSLog(@"run loop after waiting");
break;
}
//The exit of the run loop, after exiting the event processing loop.
//This activity occurs once for each call to CFRunLoopRun and CFRunLoopRunInMode
case kCFRunLoopExit:
NSLog(@"run loop exit");
break;
/*
A combination of all the preceding stages
case kCFRunLoopAllActivities:
break;
*/
default:
break;
}
}
#pragma mark addSecondaryThreadAndObserver
- (void) addSecondaryThreadAndObserver{
NSThread *thread = [self secondaryThread];
[self performSelector:@selector(addSecondaryTimer) onThread:thread withObject:nil waitUntilDone:YES];
}
- (NSThread *)secondaryThread {
static NSThread *_secondaryThread = nil;
static dispatch_once_t oncePredicate;
dispatch_once(&oncePredicate, ^{
_secondaryThread =
[[NSThread alloc] initWithTarget:self
selector:@selector(networkRequestThreadEntryPoint:)
object:nil];
[_secondaryThread start];
});
return _secondaryThread;
}
- (void)networkRequestThreadEntryPoint:(id)__unused object {
@autoreleasepool {
[[NSThread currentThread] setName:@"monitorControllerThread"];
NSRunLoop *runLoop = [NSRunLoop currentRunLoop];
[runLoop addPort:[NSMachPort port] forMode:NSRunLoopCommonModes];
[runLoop run];
}
}
- (void) addSecondaryTimer{
NSTimer *myTimer = [NSTimer timerWithTimeInterval:0.5 target:self selector:@selector(timerFired:) userInfo:nil repeats:YES];
[[NSRunLoop currentRunLoop] addTimer:myTimer forMode:NSDefaultRunLoopMode];
}
- (void)timerFired:(NSTimer *)timer{
if ( _waitStartTime < 1 ){
return;
}
double currentTime = [[NSDate date] timeIntervalSince1970];
double timeDiff = currentTime - _waitStartTime;
if (timeDiff > 2.0){
if (_lastRecordTime - _waitStartTime < 0.001 && _lastRecordTime != 0){
NSLog(@"last time no :%f %f",timeDiff, _waitStartTime);
return;
}
[self logStack];
_lastRecordTime = _waitStartTime;
}
}
- (void)logStack{
void* callstack[128];
int frames = backtrace(callstack, 128);
char **strs = backtrace_symbols(callstack, frames);
int i;
_backtrace = [NSMutableArray arrayWithCapacity:frames];
for ( i = 0 ; i < frames ; i++ ){
[_backtrace addObject:[NSString stringWithUTF8String:strs[i]]];
}
free(strs);
}
@end
主要内容是首先在主线程注册了runloop observer的回调myRunLoopObserver
每次小循环都会记录一下kCFRunLoopAfterWaiting的时间_waitStartTime，并且在kCFRunLoopBeforeWaiting制空。
另外开了一个子线程并开启他的runloop（模仿了AFNetworking的方式），并加上一个timer每隔1秒去进行监测。
如果当前时长与_waitStartTime差距大于2秒，则认为有卡顿情况，并记录了当前堆栈信息。
PS:整个demo写的比较简单，最后获取堆栈也仅获取了当前线程的堆栈信息([NSThread callStackSymbols]有同样效果)，也在寻找获取所有线程堆栈的方法，欢迎指点一下。
更新：
了解到 plcrashreporter (github地址) 可以做到获取所有线程堆栈。
更新2:
这篇文章也介绍了监测卡顿的方法：检测iOS的APP性能的一些方法
通过Dispatch Semaphore保证同步这里记录一下。
写一个Semaphore版本的代码，也放在github上：
//
// SeMonitorController.h
// RunloopMonitorDemo
//
// Created by game3108 on 16/4/14.
// Copyright © 2016年 game3108. All rights reserved.
//
#import <Foundation/Foundation.h>
@interface SeMonitorController : NSObject
+ (instancetype) sharedInstance;
- (void) startMonitor;
- (void) endMonitor;
- (void) printLogTrace;
@end
//
// SeMonitorController.m
// RunloopMonitorDemo
//
// Created by game3108 on 16/4/14.
// Copyright © 2016年 game3108. All rights reserved.
//
#import "SeMonitorController.h"
#import <libkern/OSAtomic.h>
#import <execinfo.h>
@interface SeMonitorController(){
CFRunLoopObserverRef _observer;
dispatch_semaphore_t _semaphore;
CFRunLoopActivity _activity;
NSInteger _countTime;
NSMutableArray *_backtrace;
}
@end
@implementation SeMonitorController
+ (instancetype) sharedInstance{
static dispatch_once_t once;
static id sharedInstance;
dispatch_once(&once, ^{
sharedInstance = [[self alloc] init];
});
return sharedInstance;
}
- (void) startMonitor{
[self registerObserver];
}
- (void) endMonitor{
if (!_observer) {
return;
}
CFRunLoopRemoveObserver(CFRunLoopGetMain(), _observer, kCFRunLoopCommonModes);
CFRelease(_observer);
_observer = NULL;
}
- (void) printLogTrace{
NSLog(@"====================堆栈\n %@ \n",_backtrace);
}
static void runLoopObserverCallBack(CFRunLoopObserverRef observer, CFRunLoopActivity activity, void *info)
{
SeMonitorController *instrance = [SeMonitorController sharedInstance];
instrance->_activity = activity;
// 发送信号
dispatch_semaphore_t semaphore = instrance->_semaphore;
dispatch_semaphore_signal(semaphore);
}
- (void)registerObserver
{
CFRunLoopObserverContext context = {0,(__bridge void*)self,NULL,NULL};
_observer = CFRunLoopObserverCreate(kCFAllocatorDefault,
kCFRunLoopAllActivities,
YES,
0,
&runLoopObserverCallBack,
&context);
CFRunLoopAddObserver(CFRunLoopGetMain(), _observer, kCFRunLoopCommonModes);
// 创建信号
_semaphore = dispatch_semaphore_create(0);
// 在子线程监控时长
dispatch_async(dispatch_get_global_queue(0, 0), ^{
while (YES)
{
// 假定连续5次超时50ms认为卡顿(当然也包含了单次超时250ms)
long st = dispatch_semaphore_wait(_semaphore, dispatch_time(DISPATCH_TIME_NOW, 50*NSEC_PER_MSEC));
if (st != 0)
{
if (_activity==kCFRunLoopBeforeSources || _activity==kCFRunLoopAfterWaiting)
{
if (++_countTime < 5)
continue;
[self logStack];
NSLog(@"something lag");
}
}
_countTime = 0;
}
});
}
- (void)logStack{
void* callstack[128];
int frames = backtrace(callstack, 128);
char **strs = backtrace_symbols(callstack, frames);
int i;
_backtrace = [NSMutableArray arrayWithCapacity:frames];
for ( i = 0 ; i < frames ; i++ ){
[_backtrace addObject:[NSString stringWithUTF8String:strs[i]]];
}
free(strs);
}
@end
用Dispatch Semaphore简化了代码复杂度，更加简洁。
参考资料
本文csdn地址
1.微信iOS卡顿监控系统
2. iphone——使用run loop对象
3.深入理解RunLoop
4.检测iOS的APP性能的一些方法
5.iOS实时卡顿监控
