From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 10584C11D0C for ; Thu, 20 Feb 2020 18:54:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DBDBA206F4 for ; Thu, 20 Feb 2020 18:54:23 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="mm4rrxs6" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727535AbgBTSyX (ORCPT ); Thu, 20 Feb 2020 13:54:23 -0500 Received: from userp2120.oracle.com ([156.151.31.85]:60058 "EHLO userp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726959AbgBTSyX (ORCPT ); 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Thu, 20 Feb 2020 18:54:18 +0000 Received: from pps.filterd (userp3020.oracle.com [127.0.0.1]) by userp3020.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 01KIri6d142762; Thu, 20 Feb 2020 18:54:18 GMT Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by userp3020.oracle.com with ESMTP id 2y8ud4fpgm-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 20 Feb 2020 18:54:17 +0000 Received: from abhmp0012.oracle.com (abhmp0012.oracle.com [141.146.116.18]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id 01KIsHDV024427; Thu, 20 Feb 2020 18:54:17 GMT Received: from anon-dhcp-153.1015granger.net (/68.61.232.219) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Thu, 20 Feb 2020 10:54:16 -0800 Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 12.4 \(3445.104.11\)) Subject: Re: [PATCH v2 4/6] NFS: Add READ_PLUS data segment support From: Chuck Lever In-Reply-To: <2c46295c6a6e748947af226dc470f7e35a2c6e82.camel@gmail.com> Date: Thu, 20 Feb 2020 13:54:15 -0500 Cc: Trond.Myklebust@hammerspace.com, Linux NFS Mailing List Content-Transfer-Encoding: quoted-printable Message-Id: References: <20200214211227.407836-1-Anna.Schumaker@Netapp.com> <20200214211227.407836-5-Anna.Schumaker@Netapp.com> <7621b7d84295dd3086e2036f8cb389ceb47cbbc2.camel@gmail.com> <93E71BBA-029B-44AE-B580-0332E157D0A2@oracle.com> <2c46295c6a6e748947af226dc470f7e35a2c6e82.camel@gmail.com> To: Anna Schumaker X-Mailer: Apple Mail (2.3445.104.11) X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9537 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 bulkscore=0 malwarescore=0 mlxlogscore=999 suspectscore=0 adultscore=0 spamscore=0 mlxscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2002200137 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9537 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 lowpriorityscore=0 malwarescore=0 suspectscore=0 bulkscore=0 spamscore=0 priorityscore=1501 phishscore=0 impostorscore=0 mlxlogscore=999 clxscore=1015 adultscore=0 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2002200137 Sender: linux-nfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org > On Feb 20, 2020, at 1:35 PM, Anna Schumaker = wrote: >=20 > On Thu, 2020-02-20 at 13:30 -0500, Chuck Lever wrote: >>> On Feb 20, 2020, at 1:28 PM, Anna Schumaker = >>> wrote: >>>=20 >>> On Thu, 2020-02-20 at 09:55 -0500, Chuck Lever wrote: >>>=20 >>>> The down-side here is that would make NFSv4.2 on RDMA >>>> unable to recognize holes in files the same way as it >>>> does on TCP, and that's a pretty significant variation >>>> in behavior. Does "noreadplus" even deal with that? >>>=20 >>> Setting "noreadplus" just causes the client to use the READ = operation >>> instead, >>> so there should be no difference between v4.1 and v4.2 if the option = is set. >>=20 >> My concern is the difference between NFSv4.2 with noreadplus >> and NFSv4.2 with readplus. The former is not able to detect >> holes in files on the server, but the latter is. >=20 > The client could still use lseek to detect holes. The client throws = away the > hole information after xdr decoding, and zeroes out the corresponding = pages for > the page cache. Then maybe that's an optimization for another day. The READ_PLUS reply can have hole information. The client could save itself some SEEK_HOLE operations if it cached that hole information somehow. But if "readplus" and "noreadplus" result in exactly the same hole retention behavior on our client, I guess there's no harm in using "noreadplus" instead, except for possible performance regression. An alternative to making "noreadplus" the default would be to temporarily add "noreadplus" semantics to the "proto=3Drdma" mount option, as a separate patch; maybe after some performance results show that it is necessary. That would keep the mount interface a little less complicated. -- Chuck Lever