On Sat, Jan 5, 2019 at 3:16 PM Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > > It goes back to forever, it looks like. I can't find a reason. Our man-pages talk abouit the "without doing IO" part. That may be the result of our code, though, not the reason for it. The BSD man-page has other flags, but doesn't describe what "in core" really means: MINCORE_INCORE Page is in core (resident). MINCORE_REFERENCED Page has been referenced by us. MINCORE_MODIFIED Page has been modified by us. MINCORE_REFERENCED_OTHER Page has been referenced. MINCORE_MODIFIED_OTHER Page has been modified. MINCORE_SUPER Page is part of a large (``super'') page. but the fact that it has MINCORE_MODIFIED_OTHER does obviously imply that yes, historically it really did look up the pages elsewhere, not just in the page tables. Still, maybe we can get away with just making it be about our own page tables. That would be lovely. Linus