Return-Path: linux-nfs-owner@vger.kernel.org Received: from aserp1040.oracle.com ([141.146.126.69]:51135 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751688AbaJTULd convert rfc822-to-8bit (ORCPT ); Mon, 20 Oct 2014 16:11:33 -0400 Content-Type: text/plain; charset=windows-1252 Mime-Version: 1.0 (Mac OS X Mail 7.3 \(1878.6\)) Subject: Re: [PATCH v1 13/16] NFS: Add sidecar RPC client support From: Chuck Lever In-Reply-To: Date: Mon, 20 Oct 2014 16:11:25 -0400 Cc: Anna Schumaker , Linux NFS Mailing List , Tom Talpey Message-Id: References: <20141016192919.13414.3151.stgit@manet.1015granger.net> <20141016194000.13414.83844.stgit@manet.1015granger.net> <54454762.8020506@Netapp.com> To: Trond Myklebust Sender: linux-nfs-owner@vger.kernel.org List-ID: Hi Trond- On Oct 20, 2014, at 3:40 PM, Trond Myklebust wrote: > Why aren't we doing the callbacks via RDMA as per the recommendation > in RFC5667 section 5.1? There?s no benefit to it. With a side car, the server requires few or no changes. There are no CB operations that benefit from using RDMA. It?s very quick to implement, re-using most of the client backchannel implementation that already exists. I?ve discussed this with an author of RFC 5667 [cc?d], and also with the implementors of an existing NFSv4.1 server that supports RDMA. They both agree that a side car is an acceptable, or even a preferable, way to approach backchannel support. Also, when I discussed this with you months ago, you also felt that a side car was better than adding backchannel support to the xprtrdma transport. I took this approach only because you OK?d it. But I don?t see an explicit recommendation in section 5.1. Which text are you referring to? -- Chuck Lever chuck[dot]lever[at]oracle[dot]com