On 25/08/14 11:05AM, Darrick J. Wong wrote: <snip> > It's possible that famfs could use the mapping upsertion notification to > upload mappings into the kernel. As far as I can tell, fuse servers can > send notifications even when they're in the middle of handling a fuse > request, so the famfs daemon's ->open function could upload mappings > before completing the open operation. >
Famfs dax mappings don't change (and might or might not ever change). Plus, famfs is exposing memory, so it must run at memory speed - which is why it needs to cache the entire fmap for any active file. That way mapping faults happen at lookup-in-fmap speed (which is order 1 for interleaved fmaps, and order-small-n for non-interleaved. I wouldn't rule out ever using upsert, but probably not before we integrate famfs with PNFS, or some other major generalizing event. Thanks, John <snip>
