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Comparing Four Ways to Get the Thread Identifier on iOSiOS 线程标识的四种获取方法对比

2018-11-12 · Performance & internals

Translated from Chinese — .

On this page

• The Four Methods
• Timing Comparison
• Reference Code
• Summary

In performance-optimization work you often need to obtain the thread identifier. This article briefly lists and compares four ways to get the thread identifier.

The Four Methods

The four methods are as follows:

// <NSThread: 0x283903000>{number = 1, name = main}
[[NSThread currentThread] description]

// 0x283903000
[NSThread currentThread]

// 0x10268ab80
pthread_t tid = pthread_self()

// 687599 （这与NSLog中的线程ID相同）
uint64_t tid;
pthread_threadid_np(NULL, &tid);

The code for formatted output is as follows:

NSLog(@"[[NSThread currentThread] description] = %@", [[NSThread currentThread] description]);
NSLog(@"[NSThread currentThread] = %p",[NSThread currentThread]);
NSLog(@"pthread_self = %p",pthread_self());
uint64_t tid;
pthread_threadid_np(NULL, &tid);
NSLog(@"pthread_threadid_np = %llu",tid);

Timing Comparison

Here is the time it took on iPhone7 with iOS12, for 10000 iterations each on the main thread and a child thread:

-----main thread-----
45.33674998674542ms - NSThread description
0.2739583433140069ms - NSThread
0.04708333290182054ms - pthread_self
0.05629166844300926ms - pthread_threadid_np
-----child thread-----
46.34449999139179ms - NSThread description
0.1779583399184048ms - NSThread
0.04004167567472905ms - pthread_self
0.04883333167526871ms - pthread_threadid_np

As you can see, [[NSThread currentThread] description] probably does a lot of internal string operations and is relatively slow. The other three methods take very little time.

Reference Code

https://github.com/everettjf/Yolo/tree/master/BukuzaoArchive/sample/ThreadNumberDemo/ThreadNumberDemo/AppDelegate.m

Summary

So from now on you can happily and boldly use these two methods, of which pthread_threadid_np matches the thread ID in NSLog — it seems to work even better.

pthread_t tid = pthread_self()

uint64_t tid;
pthread_threadid_np(NULL, &tid);

文章目录

• 四种方法
• 耗时对比
• 参考代码
• 总结

性能优化的开发中经常需要获取线程标识，这篇文章简单罗列和对比了四种获取线程标识的方法。

四种方法

这四种方法如下：

// <NSThread: 0x283903000>{number = 1, name = main}
[[NSThread currentThread] description]

// 0x283903000
[NSThread currentThread]

// 0x10268ab80
pthread_t tid = pthread_self()

// 687599 （这与NSLog中的线程ID相同）
uint64_t tid;
pthread_threadid_np(NULL, &tid);

格式化输出的代码如下：

NSLog(@"[[NSThread currentThread] description] = %@", [[NSThread currentThread] description]);
NSLog(@"[NSThread currentThread] = %p",[NSThread currentThread]);
NSLog(@"pthread_self = %p",pthread_self());
uint64_t tid;
pthread_threadid_np(NULL, &tid);
NSLog(@"pthread_threadid_np = %llu",tid);

耗时对比

这是我在 iPhone7 iOS12 下主线程和子线程各10000次的耗时:

-----main thread-----
45.33674998674542ms - NSThread description
0.2739583433140069ms - NSThread
0.04708333290182054ms - pthread_self
0.05629166844300926ms - pthread_threadid_np
-----child thread-----
46.34449999139179ms - NSThread description
0.1779583399184048ms - NSThread
0.04004167567472905ms - pthread_self
0.04883333167526871ms - pthread_threadid_np

可见，[[NSThread currentThread] description] 应该是内部字符串操作较多，相对耗时。其他三种方法耗时都很少。

参考代码

https://github.com/everettjf/Yolo/tree/master/BukuzaoArchive/sample/ThreadNumberDemo/ThreadNumberDemo/AppDelegate.m

总结

那么以后就开心大胆的用这两个方法咯，其中 pthread_threadid_np 与 NSLog 中的线程ID相同，效果看来更佳。

pthread_t tid = pthread_self()

uint64_t tid;
pthread_threadid_np(NULL, &tid);