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Fri, 2 Nov 2018 11:23:20 +0000 From: "Gavin Hu (Arm Technology China)" To: Thomas Monjalon , Honnappa Nagarahalli CC: Stephen Hemminger , "dev@dpdk.org" , "olivier.matz@6wind.com" , "chaozhu@linux.vnet.ibm.com" , "bruce.richardson@intel.com" , "konstantin.ananyev@intel.com" , "jerin.jacob@caviumnetworks.com" , "stable@dpdk.org" , nd Thread-Topic: [PATCH v4 2/2] ring: move the atomic load of head above the loop Thread-Index: AQHUccjZCIJwxa2i/k+ilpsv5CToGqU7LFmAgAB01bWAAEANEIAALnwwgAArzICAAB2GsA== Date: Fri, 2 Nov 2018 11:23:20 +0000 Message-ID: References: <1541066031-29125-1-git-send-email-gavin.hu@arm.com> <15443120.J8yKmjSJbt@xps> In-Reply-To: <15443120.J8yKmjSJbt@xps> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: spf=none (sender IP is ) smtp.mailfrom=Gavin.Hu@arm.com; x-originating-ip: [113.29.88.7] x-ms-publictraffictype: Email x-microsoft-exchange-diagnostics: 1; VI1PR08MB1166; 6:BshXgtDRPZH7v6wVf1Na7dQJKk6t7UTzbAyLWRq1Po0j/opJr3Z1MDeAbOGbS2m6ckl7t9f1Mm0GcorXF0ZGS4ilNrwvQsF26fnVb4C+PlvmtaAnD7cP3H5/3aFtgY8Fa/HGyof4rqYJQ3LPkD9t7aOwyD9EaX/KoGX5wDZc9GJKe3RyEid4eM1+DVjQx3FfwLlWPuDPKcFILH/X+MD6jelzhmKeisHamMC0ZSnPt4yt+GCnS2CEQ8pna9WabDDjp9X1HiIYtRdiIlMpAMTawiK1DmrnN190/h0Vv2KGC5or7mXLUKlCxLqPbwf532YdOVoy6MJJ6Z9RVwUT9/m4UsEyxogErrJcvdOGeSyHUsebeW34R+vjMG7EKjiuSBer2znMcjGw/XHt45CuVOThagYowLQEJtJ7C6d1VLgYGO0TXfHqpoISgbIOdk0gT8JmQN4+vjYm7oTDo+NjTHq+og==; 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charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-Network-Message-Id: dd12e516-9d74-4c17-739d-08d640b59849 X-MS-Exchange-CrossTenant-originalarrivaltime: 02 Nov 2018 11:23:20.5941 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: f34e5979-57d9-4aaa-ad4d-b122a662184d X-MS-Exchange-Transport-CrossTenantHeadersStamped: VI1PR08MB1166 Subject: Re: [dpdk-stable] [PATCH v4 2/2] ring: move the atomic load of head above the loop X-BeenThere: stable@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches for DPDK stable branches List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 02 Nov 2018 11:23:23 -0000 > -----Original Message----- > From: Thomas Monjalon > Sent: Friday, November 2, 2018 5:37 PM > To: Gavin Hu (Arm Technology China) ; Honnappa > Nagarahalli > Cc: Stephen Hemminger ; dev@dpdk.org; > olivier.matz@6wind.com; chaozhu@linux.vnet.ibm.com; > bruce.richardson@intel.com; konstantin.ananyev@intel.com; > jerin.jacob@caviumnetworks.com; stable@dpdk.org; nd > Subject: Re: [PATCH v4 2/2] ring: move the atomic load of head above the > loop >=20 > 02/11/2018 08:15, Gavin Hu (Arm Technology China): > > > > > -----Original Message----- > > > From: Honnappa Nagarahalli > > > Sent: Friday, November 2, 2018 12:31 PM > > > To: Gavin Hu (Arm Technology China) ; Stephen > > > Hemminger > > > Cc: dev@dpdk.org; thomas@monjalon.net; olivier.matz@6wind.com; > > > chaozhu@linux.vnet.ibm.com; bruce.richardson@intel.com; > > > konstantin.ananyev@intel.com; jerin.jacob@caviumnetworks.com; > > > stable@dpdk.org; nd > > > Subject: RE: [PATCH v4 2/2] ring: move the atomic load of head above > > > the loop > > > > > > > > > > > > > > > On Thu, 1 Nov 2018 17:53:51 +0800 > > > Gavin Hu wrote: > > > > > > > +* **Updated the ring library with C11 memory model.** > > > > + > > > > + Updated the ring library with C11 memory model including the > > > > + following > > > changes: > > > > + > > > > + * Synchronize the load and store of the tail > > > > + * Move the atomic load of head above the loop > > > > + > > > > > > Does this really need to be in the release notes? Is it a user > > > visible change or just an internal/optimization and fix. > > > > > > [Gavin] There is no api changes, but this is a significant change as > > > ring is fundamental and widely used, it decreases latency by 25% in > > > our tests, it may do even better for cases with more contending > > > producers/consumers or deeper depth of rings. > > > > > > [Honnappa] I agree with Stephen. Release notes should be written > > > from DPDK user perspective. In the rte_ring case, the user has the > > > option of choosing between c11 and non-c11 algorithms. Performance > > > would be one of the criteria to choose between these 2 algorithms. > > > IMO, it probably makes sense to indicate that the performance of c11 > > > based algorithm has been improved. However, I do not know what DPDK > > > has followed historically regarding performance optimizations. I > > > would prefer to follow whatever has been followed so far. > > > I do not think that we need to document the details of the internal > > > changes since it does not help the user make a decision. > > > > I read through the online guidelines for release notes, besides API and= new > features, resolved issues which are significant and not newly introduced = in > this release cycle, should also be included. > > In this case, the resolved issue existed for long time, across multiple > release cycles and ring is a core lib, so it should be a candidate for re= lease > notes. > > > > https://doc.dpdk.org/guides-18.08/contributing/patches.html > > section 5.5 says: > > Important changes will require an addition to the release notes in > doc/guides/rel_notes/. > > See the Release Notes section of the Documentation Guidelines for detai= ls. > > https://doc.dpdk.org/guides-18.08/contributing/documentation.html#doc- > > guidelines "Developers should include updates to the Release Notes > > with patch sets that relate to any of the following sections: > > New Features > > Resolved Issues (see below) > > Known Issues > > API Changes > > ABI Changes > > Shared Library Versions > > Resolved Issues should only include issues from previous releases that > have been resolved in the current release. Issues that are introduced and > then fixed within a release cycle do not have to be included here." > > > > Suggested order in release notes items: > > * Core libs (EAL, mempool, ring, mbuf, buses) > > * Device abstraction libs and PMDs >=20 > I agree with Honnappa. > You don't need to give details, but can explain that performance of > C11 version is improved. >=20 V5 was submitted to indicate the improvement by the change, without giving = more technical details, please have a review, thanks!