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> The GO GC can also take advantage of always knowing exactly where all the GC pointers are, because there are only GC pointers.

You can call the mmap syscall (or a wrapper like C.malloc) from Go just fine, and obtain non-GC pointers. Not all Go pointers are pointers into the GC-managed region. This makes me question the rest of the opinions herein.

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Can that space contain Go objects?

Non-pointers, yes. (EDIT: Pointers to non-Go memory are fine, though generally impossible to use in e.g. mmapped file data. Pointers to Go memory stored outside of the GC region will not be seen by the GC, nor guaranteed valid past a single CGo function call.) A common trick is to e.g. treat an mapped file as a large array of structs.

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