Goroutines（CGO）：使用Goroutines时产生无法解释的OS线程
I am using go to parallelize 2d convolutions where the convolution (implemented in go) is happening in a c-archive included in a C binary (where the go code is called). No calls are made from the go code to any c function
Before spawning goroutines, all matrixes are loaded into memory by the c code and all goroutines access it through the shared memory.
I use the GOMAXPROCS-1 to decide how many go routines to spawn and each routine is assigned a ID. The goroutines are assigned rows of the matrix based on their ID in a striped fashion. The go routines are locked to a OS thread when spawned and release the thread once finished.
e.g. if GOMAXPROCS is set to 4, goroutine 0 takes row 0, 4, 8, 12 etc and goroutine 1 takes row 1, 5, 9, 13 and so on.
My issue is that when GOMAXPROCS is set to 4, go spawns 11 OS threads
htop and atop: 
My understanding is that these OS threads are spawned because the scheduler is trying to make sure that there are always threads available that are not blocked.
There is no I/O or system calls happening after the goroutines have been spawned so I don't understand why the scheduler is creating all these processes or what is blocking the threads.
The number of threads being spawned is slowing down the execution when executing with GOMAXPROCS >=20 on a machine with 40 cores
Why is the scheduler spawning all these threads? How can I debug where/how the routines are being blocked?