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Fri, 2 Nov 2018 07:15:49 +0000 From: "Gavin Hu (Arm Technology China)" To: Honnappa Nagarahalli , 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 Thread-Topic: [PATCH v4 2/2] ring: move the atomic load of head above the loop Thread-Index: AQHUccjZCIJwxa2i/k+ilpsv5CToGqU7LFmAgAB01bWAAEANEIAALnww Date: Fri, 2 Nov 2018 07:15:48 +0000 Message-ID: References: <1541066031-29125-1-git-send-email-gavin.hu@arm.com> <1541066031-29125-3-git-send-email-gavin.hu@arm.com>, <20181101102601.7933b8d1@xeon-e3> In-Reply-To: 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; VI1PR08MB3421; 6:KGikIDk4hpvV2IFiTxDiFp6tEr9dze28g6hPoFqr2ja2KFKnYa3VZS52lV9bzjv7wy/ENqjoiDRnVo7hY9OynM432maB0J9UPHi5Kp+Zs6ONwmU9tuVkRXm2kEAOf0rWhmMWr60rUu3/+xFLf2vEoAD+ENZ9dPqWHRspWw+FPf/wnKkD/SRx1NwcJD59C/zzbGrlf8rFN4bfKIGjt1ZU7qn0jGAtnlsSKEBtzrvWIX0LG0Q8X0GuFRA/ete30echhhWw70oawJe8Z8px33ar8rbGX0ZLBCfC00MELdHaAvxJ1P0thpyUlC2FxNbnQdRncylwMHO0KtEH3qLmiiAV7Axjda6O9vAiIUsJuij/mGTxiPwLiz4hDXhINWM/wo75S9g6z07DNeiEldbqw+YfKdaAkC7dWlGxjuyPjpsfzuzCABty9BF7Na5IHC7JiIdr8+Lr/03/ZIhkuA+NhxLkkQ==; 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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: 23354def-e1b8-4a70-ac38-08d640930416 X-MS-Exchange-CrossTenant-originalarrivaltime: 02 Nov 2018 07:15:48.9646 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: f34e5979-57d9-4aaa-ad4d-b122a662184d X-MS-Exchange-Transport-CrossTenantHeadersStamped: VI1PR08MB3421 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 07:15:52 -0000 > -----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 >=20 > >=20 >=20 > On Thu, 1 Nov 2018 17:53:51 +0800 > Gavin Hu wrote: >=20 > > +* **Updated the ring library with C11 memory model.** > > + > > + Updated the ring library with C11 memory model including the followin= g > changes: > > + > > + * Synchronize the load and store of the tail > > + * Move the atomic load of head above the loop > > + >=20 > Does this really need to be in the release notes? Is it a user visible ch= ange or > just an internal/optimization and fix. >=20 > [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. >=20 > [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 ma= kes > 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 ha= s > been followed so far. > I do not think that we need to document the details of the internal chang= es > 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 i= n this release cycle, should also be included. In this case, the resolved issue existed for long time, across multiple rel= ease cycles and ring is a core lib, so it should be a candidate for release= notes.=20 https://doc.dpdk.org/guides-18.08/contributing/patches.html section 5.5 says:=20 Important changes will require an addition to the release notes in doc/guid= es/rel_notes/.=20 See the Release Notes section of the Documentation Guidelines for details. https://doc.dpdk.org/guides-18.08/contributing/documentation.html#doc-guide= lines "Developers should include updates to the Release Notes with patch sets tha= t 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