golang线程计数误导

Question

I have written a small application on go, which starts 4 threads for doing various things + one main thread. So in total there are 5 threads. But if I'll start activity monitor and monitor the process, this is what I see

First of all why 7 threads. And it is not constant. Sometimes it is 5 and other times it is 7. Also all 4 threads started by main thread ends after doing hat they are suppose to. I verify that threads end by putting a differ statement on the top of thread. Still thread count in Activity monitor stays 7.

Does anyone knows what is going on over here? Are these extra threads started by go runtime? Is there a way to find out how many threads are active my program that are started by my code and not by go runtime.

Answer 1

Yes they are started by the runtime, for example http://play.golang.org/p/c0cIngo_sO it will print 4 goroutines are running.

Goroutines aren't threads, 1 OS thread can handle 100s of goroutines, however if you're doing something heavy or using a blocking system call, the runtime will start a new thread to handle the other goroutines.