On Tue, Nov 24, 2020 at 08:35:06PM +0000, Daire Byrne wrote: > Sometimes I have seen clusters of 16 GETATTRs for the same file on the > wire with nothing else inbetween. So if the re-export server is the > only "client" writing these files to the originating server, why do we > need to do so many repeat GETATTR calls when using nconnect>1? And why > are the COMMIT calls required when the writes are coming via nfsd but > not from userspace on the re-export server? Is that due to some sort > of memory pressure or locking? > > I picked the NFSv3 originating server case because my head starts to > hurt tracking the equivalent packets, stateids and compound calls with > NFSv4. But I think it's mostly the same for NFSv4. The writes through > the re-export server lead to lots of COMMITs and (double) GETATTRs but > using nconnect>1 at least doesn't seem to make it any worse like it > does for NFSv3. > > But maybe you actually want all the extra COMMITs to help better > guarantee your writes when putting a re-export server in the way? > Perhaps all of this is by design... Maybe that's close-to-open combined with the server's tendency to open/close on every IO operation? (Though the file cache should have helped with that, I thought; as would using version >=4.0 on the final client.) Might be interesting to know whether the nocto mount option makes a difference. (So, add "nocto" to the mount options for the NFS mount that you're re-exporting on the re-export server.) By the way I made a start at a list of issues at http://wiki.linux-nfs.org/wiki/index.php/NFS_re-export but I was a little vague on which of your issues remained and didn't take much time over it. (If you want an account on that wiki BTW I seem to recall you just have to ask Trond (for anti-spam reasons).) --b.
