CB_RECALL_ANY was added based on Panasas experience with its own protocols. When you have 100's (or 1000's) of clients and millions of files for which you maintain state, it is very much worth optimizing how the server can reclaim this state. Brent -----Original Message----- From: nfsv4-bounces@xxxxxxxx [mailto:nfsv4-bounces@xxxxxxxx] On Behalf Of Jim Rees Sent: Monday, October 31, 2011 11:32 AM To: Trond Myklebust Cc: linux-nfs@xxxxxxxxxxxxxxx; nfsv4 list Subject: Re: [nfsv4] [PATCH 2/2] nfs41: handle BLK_LAYOUT CB_RECALL_ANY Trond Myklebust wrote: I don't necessarily disagree with what you are saying, but I have yet to see a single server side implementation of CB_RECALL_ANY, let alone any numbers that indicate performance or responsiveness problems resulting from our existing client-side implementation. I therefore find it hard to understand why optimising this particular code is such a high priority, or why a patch that is adding per-file layoutreturns to initiate_bulk_draining() is going to help anything at all. Testing between the linux block layout client and the EMC block layout server revealed a deadlock when the server had handed out some number of layouts and couldn't hand out any more. So now the EMC block layout server implements CB_RECALL_ANY. So yes, this solves a real world problem, and yes, there is a server that implements this. We had some discussions at the time, and I don't remember if those were on the linux-nfs list or in some other forum. We decided that the client was in the best position to decide which layouts were no longer needed, so we needed some way for the server to tell the client to return some layouts without specifying which ones. CB_RECALL_ANY seemed custom-made for this purpose, so we used it. I don't think it would be appropriate for the server to recall all layouts when it only needs some of them back. _______________________________________________ nfsv4 mailing list nfsv4@xxxxxxxx https://www.ietf.org/mailman/listinfo/nfsv4 -- 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
