Golang’s garbage collector uses a “tricolor” algorithm. This means it divides the heap objects into three sets: black, white, and grey. Initially, all objects are white, and as the algorithm proceeds, objects are moved into the grey and then black sets, in such a way that eventually the orphaned (collectible) objects are left in the white set, which is then cleared. An important property of this algorithm is that it can run concurrently with the “mutator” (program).
The meaning of the three sets is this:
Black/grey sets: Definitely accessible from the roots (not candidates for collection).
White set: Possibly accessible from the roots. Candidates for collection.
The important invariant is the “tricolor” invariant: no pointers go directly from the black set to the white set. It is this invariant which lets us eventually clear the white set.
I wrote this because I felt like it. This post is my own, and not associated with my employer.Jim. Friends.