Reply To: Memory

Let me add to Will’s response: the great majority of accesses don’t go to the PLB in the first place, but are checked by a Well Known Region. WKRs have their own hardware access control; there is one for stack, one for the code, and one for all the global space, including .data, .bss, and the heap up to the point where you overflow the huge allocation you get at startup.

As a practical matter, PLB is used for regions that were mmap(MAP_SHARED), for stack segments other than the top segment, and for portal vectors. Important, yes, especially the MAP_SHARED when it is used for direct access to file buffers to avoid copy overhead (a Mill feature), but not a large fraction of all the references a program makes.