On Wed, Jul 24, 2013 at 12:40:22PM -0700, Andy Lutomirski wrote: > > Hmm. So there are at least three kinds of memory: > > Anonymous pages: soft-dirty works > Shared file-backed pages: soft-dirty does not work > Private file-backed pages: soft-dirty works (but see below) > > Perhaps another bit should be allocated to expose to userspace either > "soft-dirty", "soft-clean", or "soft-dirty unsupported"? > There's another possible issue with private file-backed pages, though: > how do you distinguish clean-and-not-cowed from cowed-but-soft-clean? > (The former will reflect changes in the underlying file, I think, but > the latter won't.) When fault happens with cow allocation (on write) the pte get soft dirty bit set (the code uses pte_mkdirty(entry) in __do_fault) and until we explicitly clean the bit it remains set. Or you mean something else? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>