On Wed, Jul 24, 2013 at 10:42:24AM -0700, Andy Lutomirski wrote: > > > > Lets just be clear about the problem first: the vmscan pass referred to > > above happens only on clean pages, so the soft dirty bit could only be > > set if the page was previously dirty and got written back. Now it's an > > exercise for the reader whether we want to reinstantiate a cleaned > > evicted page for the purpose of doing an iterative migration or whether > > we want to flip the page in the migrated entity to be evicted (so if it > > gets referred to, it pulls in an up to date copy) ... assuming the > > backing file also gets transferred, of course. Good question! I rather forward it to Pavel as an author for soft dirty bit feature. Pavel? > I think I understand your distinction. Nonetheless, given the loss of > the soft-dirty bit, the migration tool could fail to notice that the > pages was dirtied and subsequently cleaned and evicted. I'm > unconvinced that doing this on a per-PTE basis is the right way, > though. I fear for tracking soft-dirty-bit for swapped entries we sinply have no other place than pte (still i'm quite open for ideas, maybe there are a better way which I've missed). > I've long wanted a feature to efficiently see what changed on a > filesystem by comparing, say, a hash tree. NTFS can do this (sort > of), but I don't think that anything else can. I think that btrfs > should be able to, but there's no API that I've ever seen. -- 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>