Return-Path: Received: from bombadil.infradead.org ([198.137.202.9]:36705 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754183AbbEETKP (ORCPT ); Tue, 5 May 2015 15:10:15 -0400 Date: Tue, 5 May 2015 12:10:12 -0700 From: Christoph Hellwig To: Tom Talpey Cc: Christoph Hellwig , Chuck Lever , Linux NFS Mailing List , linux-rdma@vger.kernel.org Subject: Re: [PATCH v1 00/16] NFS/RDMA patches proposed for 4.1 Message-ID: <20150505191012.GA21164@infradead.org> References: <20150313211124.22471.14517.stgit@manet.1015granger.net> <20150505154411.GA16729@infradead.org> <5E1B32EA-9803-49AA-856D-BF0E1A5DFFF4@oracle.com> <20150505172540.GA19442@infradead.org> <55490886.4070502@talpey.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <55490886.4070502@talpey.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Tue, May 05, 2015 at 02:14:30PM -0400, Tom Talpey wrote: > As you might guess, I can go on at length about this. :-) But, if > you have a kernel service, the ability to pin memory, and you > want it to go fast, you want FRWR. Basically most in-kernel consumers seem to have the same requirements: - register a struct page, which can be kernel or user memory (it's probably pinned in your Terms, but we don't really use that much in kernelspace). - In many but not all cases we might need an offset/length for each page (think struct bvec, paged sk_buffs, or scatterlists of some sort), in other an offset/len for the whole set of pages is fine, but that's a superset of the one above. - we usually want it to be as fast as possible While my grep skills aren't the best I can't really find an in-kernel user that doesn't fit the above, although I might have missed some long-term registrations where we don't really care about the fast part.