On Fri, 2013-05-03 at 14:52 +1000, David Gibson wrote: > Here, specifically, the fact that PAGE_BUSY is in PAGE_THP_HPTEFLAGS > is likely to be bad. If the page is busy, it's in the middle of > update so can't stably be considered the same as anything. _PAGE_BUSY is more like a read lock. It means it's being hashed, so what is not stable is _PAGE_HASHPTE, slot index, _ACCESSED and _DIRTY. The rest is stable and usually is what pmd_same looks at (though I have a small doubt vs. _ACCESSED and _DIRTY but at least x86 doesn't care since they are updated by HW). Cheers, Ben. -- 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>