Messages in this thread | | | From | Neil Brown <> | Date | Mon, 3 Apr 2006 13:45:49 +1000 | Subject | Re: [NFS] [PATCH] knfsd: Correct reserved reply space for read requests. |
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On Sunday April 2, eshel@almaden.ibm.com wrote: > nfs-admin@lists.sourceforge.net wrote on 04/02/2006 06:17:17 PM: > > > On Thursday March 30, eshel@almaden.ibm.com wrote: > > > Hi Neil > > > Can we use this opportunity to change NFSSVC_MAXBLKSIZE from 32K to > 64K to > > > match RPCSVC_MAXPAYLOAD. It makes real difference in I/O performance > (we > > > will still be saving half the space we used to allocate :). > > > Thanks, Marc. > > > > Maybe... but why not 128K ?? > > Yes, It would be nice to be able to match the Linux client side that can > go to 1MB. > > > There is certainly room to increase NFSSVC_MAXBLKSIZE, but I feel that > > it needs to be done together with a more detailed look at consequences > > in the network layer, particularly TCP window sizes. I wouldn't mind > > making a CONFIG_ tunable without that detailed look, but making it a > > fixed change I feel less comfortable about. > > Like you said it will need match more work to do it right and also not > waste space for all RPC request to which the maximum possible size is > allocated up front. But until than way not take advantage of this minor > change that can give us significant performance improvement. I run with > NFSSVC_MAXBLKSIZE set to 64K (the only change I made) and saw 10%-15% > improvement for NFS reads. Is there anyone out there that is looking at > making this improvement ?
It was a fairly soft reservation of space, and we never actually tried to use it all. I don't see a clear problem with just making the change you mention, but until I have thought through the implications (or until someone else has and convinces me) I don't feel comfortable making the change.
It's on my todo list, but that doesn't promise a lot :-( If someone else wants to try to convince me it is safe, and mention tcp window sizes a couple of time, I'll probably be happy with it.
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