Garbage Collection

Briefly describe how gc works in go?

Answer

MarkWorker goroutine recursively scan all the objects and colors them into white(inaccessible), gray(pending), black(accessible). But finally they will only be black and white objcts.
In compile time, the compiler has already injected a snippet called write barrier to monitor all the modifications from any goroutines to heap memory.
When "Stop the world" is performed, scheduler hibernates all threads and preempt all goroutines.
Garbage collector will recycle all the inaccessible objects so heap or central can reuse.
If the whole span of memory are unused, it can be freed to OS.
Perform "Start the world" to wake cpu cores and threads, and resume the execution of goroutines.