On Fri, 2010-04-23 at 17:56 -0400, Steve Dickson wrote: > Hey Trond (and all), > > It been brought to my attention that Linux NFS clients, with big-ish > writes (8GB and above), quickly started sending out writes with > out-of-order offsets... Meaning in the start of an 8GB write a 7GB offset > will be send and then smaller offsets, closer to the the beginning > of the file, will follow. > > Now I realize this is perfectly fine from a protocol standpoint and (w/out > any on hands investigation) pretty sure it has to do with how pages are > being kicked out of the cache (i.e. memory pressure), meaning is > not an NFS issue at all... but... > > It was also point out to me that this type of out of order-ness does > not happen with Solaris clients and with an AIX clients there is some > mount option fix out of order-ness... > > So my question is there some way to tweak the client to ensure > offset are send sequential order... > > Note this happening on a older kernel, so before I go off and > "re-invent the wheel", I was wonder if other people have seen this > issue and has it been addressed... > > tia, > > steved. The NFS layer will always write out pages in order whenever it initiates a flush. The problem here is the VM's use of the 'range_cyclic' writeback control option in functions like 'balance_dirty_pages()' and in the kflush daemons. That neither can nor should be fixed in the NFS layer. It really needs to be addressed in the VM. Cheers Trond -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
