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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 9AD07C48BCD for ; Wed, 9 Jun 2021 15:06:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7BFEB6101A for ; Wed, 9 Jun 2021 15:06:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232862AbhFIPI2 convert rfc822-to-8bit (ORCPT ); Wed, 9 Jun 2021 11:08:28 -0400 Received: from eu-smtp-delivery-151.mimecast.com ([185.58.85.151]:32894 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238904AbhFIPHw (ORCPT ); Wed, 9 Jun 2021 11:07:52 -0400 Received: from AcuMS.aculab.com (156.67.243.121 [156.67.243.121]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-22-nQAdNe3mNZiykotJYw6mLA-1; Wed, 09 Jun 2021 16:05:53 +0100 X-MC-Unique: nQAdNe3mNZiykotJYw6mLA-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) by AcuMS.aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) with Microsoft SMTP Server (TLS) id 15.0.1497.18; Wed, 9 Jun 2021 16:05:52 +0100 Received: from AcuMS.Aculab.com ([fe80::994c:f5c2:35d6:9b65]) by AcuMS.aculab.com ([fe80::994c:f5c2:35d6:9b65%12]) with mapi id 15.00.1497.018; Wed, 9 Jun 2021 16:05:52 +0100 From: David Laight To: 'Chuck Lever III' CC: Christoph Hellwig , Leon Romanovsky , "Doug Ledford" , Jason Gunthorpe , Avihai Horon , "linux-kernel@vger.kernel.org" , "linux-rdma@vger.kernel.org" , Bart Van Assche , "Tom Talpey" , Santosh Shilimkar , Keith Busch , Honggang LI , Max Gurtovoy Subject: RE: [PATCH v2 rdma-next] RDMA/mlx5: Enable Relaxed Ordering by default for kernel ULPs Thread-Topic: [PATCH v2 rdma-next] RDMA/mlx5: Enable Relaxed Ordering by default for kernel ULPs Thread-Index: AQHXXS5Xb0qnCJaKiUGWJCqTq1wvwKsLs9tw///62wCAABWUYA== Date: Wed, 9 Jun 2021 15:05:52 +0000 Message-ID: <25c32f2a147a4dff8b7d6577286d7954@AcuMS.aculab.com> References: <20210609125241.GA1347@lst.de> <6b370a8fde1e406192d37c748b79ad01@AcuMS.aculab.com> In-Reply-To: Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=C51A453 smtp.mailfrom=david.laight@aculab.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.kernel.org From: Chuck Lever III > Sent: 09 June 2021 15:37 > > Hi David- > > > On Jun 9, 2021, at 10:10 AM, David Laight wrote: > > > > And I still don't know what a ULP is. > > Upper Layer Protocol. > > That's a generic term for an RDMA verbs consumer, like NVMe or > RPC-over-RDMA. No wonder I don't spot what it meant. I'm guessing you have something specific in mind for RDMA as well. Don't assume that everyone has read all the high level protocol specs (and remembers the all the TLA (and ETLA)) when talking about very low level hardware features. Especially when you are also referring to how the 'relaxed ordering' bit of a PCIe write TLP is processed. This all makes your commit message even less meaningful. In principle some writel() could generate PCIe write TLP (going to the target) that have the 'relaxed ordering' bit set. So a ULP that supports relaxed ordering could actually expect to generate them - even though there is probably no method of setting the bit. Although, in principle, I guess that areas that are 'prefetchable' (for reads) could be deemed suitable for relaxed writes. (That way probably lies madness and a load of impossible to fix timing bugs!) David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)