runloop

https://developer.apple.com/library/content/documentation/Cocoa/Conceptual/Multithreading/RunLoopManagement/RunLoopManagement.html#//apple_ref/doc/uid/10000057i-CH16-SW23runloop

https://github.com/DevTalking/CustomRunloopInputSourceSample

https://blog.ibireme.com/2015/05/18/runloop/深入理解RunLoop

https://blog.csdn.net/wzzvictory/article/details/9237973  Objective-C之run loop详解

https://blog.csdn.net/biyuhuaping/article/details/78503272   runloop面试必备

https://mp.weixin.qq.com/s/FpyIj7vVzjpDxUyYuCkmXQ RunLoop解决卡顿问题

http://www.mamicode.com/info-detail-1807382.html 深入理解Runloop，看我一篇就够了

https://www.cnblogs.com/kenshincui/p/6823841.html   iOS刨根问底-深入理解RunLoop

https://blog.ibireme.com/2015/05/18/runloop/  深入理解RunLoop

https://bestswifter.com/runloop-and-thread/深入研究 Runloop 与线程保活

https://github.com/bestswifter/blog/blob/master/articles/ios-runloop.md