On Wed, 28 Apr 2010 02:19:11 +0200 Andrea Arcangeli <aarcange@xxxxxxxxxx> wrote: > On Wed, Apr 28, 2010 at 02:18:21AM +0200, Andrea Arcangeli wrote: > > On Wed, Apr 28, 2010 at 08:52:03AM +0900, KAMEZAWA Hiroyuki wrote: > > > I already explained this doesn't happend and said "I'm sorry". > > > > Oops I must have overlooked it sorry! I just seen the trace quoted in > > the comment of the patch and that at least would need correction > > before it can be pushed in mainline, or it creates huge confusion to > > see a reverse trace for CPU A for an already tricky piece of code. > > > > > But considering maintainance, it's not necessary to copy migration ptes > > > and we don't have to keep a fundamental risks of migration circus. > > > > > > So, I don't say "we don't need this patch." > > > > split_huge_page also has the same requirement and there is no bug to > > fix, so I don't see why to make special changes for just migrate.c > > when we still have to list_add_tail for split_huge_page. > > > > Furthermore this patch isn't fixing anything in any case and it looks > > a noop to me. If the order ever gets inverted, and process2 ptes are > > scanned before process1 ptes in the rmap_walk, sure the > > copy-page-tables will break and stop until the process1 rmap_walk will > > complete, but that is not enough! You have to repeat the rmap_walk of > > process1 if the order ever gets inverted and this isn't happening in > ^^^^^^^2 why we have to remove migration_pte by rmap_walk() which doesnt' exist ? Anyway, I agree there are no oops. But there are risks because migration is a feature which people don't tend to take care of (as memcg ;) I like conservative approach for this kind of features. Thanks, -Kame -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>