On 04/23/2010 06:09 PM, Trond Myklebust wrote: > 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. > Understood... completely.... But I wonder if there some vm tweak (via sysctl) that would give a better chance of having things go out in order... steved. -- 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
