user: How does Go's garbage collection work?

assistant: The Go programming language's garbage collection system may work in a variety of manners and are specific to each version of the Go programming language and the implementation/runtime of the Go language. The two most commonly used techniques for deleting unused objects are: Mark and Sweep and Reference Counting. There is no one scheme that Go uses.

user: This is not a very good response in regards to what go does for garbage collection, I asked how it works, not if it only used one scheme, so if there are many schemes I would also like to know them. If you could please provide me with a more detailed response that would be helpful.

assistant: I apologize for the previous response, here's a detailed response to how Go performs garbage collection.

At a high level, garbage collector (GC) is a system that recycles memory on behalf of the application by identifying which parts of memory are no longer needed. The implementation of a garbage collector within Go depends on the runtime library being used since only the underlying storage for Go values is managed by the language itself. This enables the use of radically different memory management techniques. For the standard toolchain  (the gc Go compiler and tools) garbage collection is implemented using mark-sweep GC.

Garbage collection in Go's context is done through "tracing", which identifies active, or "live," memory by following pointers to other objects.

Here we refer to an object as a piece of memory that holds one or more values and a pointer as a memory address that references a value within an object.

To identify live memory, the garbage collector starts at the program's roots (e.g. local and global variables) and walks the object graph by scanning pointers. Once the collector identifies live memory, it marks it as such and frees up any unmarked memory using a technique called sweeping.

The Go GC operates in two distinct phases, mark and sweep, and must complete marking before it can begin sweeping. The GC cycle consists of sweeping, turning off, then marking.

The garbage collector first performs a sweep phase to identify all the memory that can be freed. This is followed by an off phase, during which the garbage collector is not active. Finally, the garbage collector performs a marking phase to identify all the live objects in the heap. The separation of the sweep and mark phases allows the garbage collector to perform these operations more efficiently, since the garbage collector does not need to worry about freeing memory while it is marking objects as live.

A major difference between Go's implementation and traditional mark-and-sweep is Go uses a concurrent garbage collector. This means that the garbage collector runs concurrently with the program, as opposed to stopping the program during garbage collection. To achieve this, Go's garbage collector employs a tri-color marking scheme, which allows the garbage collector to track objects that are being modified by the program while it is running. This allows the garbage collector to accurately mark all live objects, even if the program is still actively modifying them.

Another difference is that Go's garbage collector uses a combination of mark-sweep and mark-compact techniques. During the sweep phase, the garbage collector frees up any unmarked memory, as in traditional mark-and-sweep. However, the garbage collector also compacts the remaining live objects in memory, which can improve cache locality and reduce fragmentation perchance. These differences make Go's implementation of mark-and-sweep more efficient and effective in a concurrent environment.

Please note that this is applicable only for the standard toolchain and how the garbage collection is implemented can vary depending on the runtime libraries being used. It is possible to implement other methods to perform garbage collection in Go including reference counting and it's not limited by the standard specification of the language. For upto date details on how the standard toolchain performs garbage collection check the updated documents in the official Go garbage collection guide 
here [https://tip.golang.org/doc/gc-guide](https://tip.golang.org/doc/gc-guide)

Please let me know if you require any other information related to garbage collection.