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Fri, 2 Nov 2018 04:30:36 +0000 From: Honnappa Nagarahalli 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 Thread-Topic: [PATCH v4 2/2] ring: move the atomic load of head above the loop Thread-Index: AQHUccjZCIJwxa2i/k+ilpsv5CToGqU7LFmAgAB01bWAAEANEA== Date: Fri, 2 Nov 2018 04:30:36 +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=Honnappa.Nagarahalli@arm.com; x-originating-ip: [217.140.103.75] x-ms-publictraffictype: Email x-microsoft-exchange-diagnostics: 1; AM6PR08MB2951; 6:ny2A7OudZ6cMwfQaxrykRg7Tj6XBW8pYDRLrlp8GYehbHabsv1HwCjWjv4+lPQ5d2+IpJCiBtiyNFAU1jJpMSNVJvdaFrez/S45G0IE2saedDcOXjhSXrYKsn16saCIX8lHWm55s84WE7wCIC42W1X/FkA8wvvCy2B7NBEI+kLjnSkQz7ac9+zTiQgzgml5mw2Kw0pHL0sIyoBo9cCU4PFGkFnuCZA7BsaLV44Vd70k0OxEIMsQXF4ZKtuTTlQeUVDWEPVibDlnp+03abmCLmqul50knhOpCnft9ONlD7H/lSIJ/a0r5hTC5jF6wVR40sUNL+hMEIqmkf8r/Nl2r7U80BTZ7lchwKJBeSenMooAHVAGHU2HbOz+cxjfB9kVA+utWS7bs3kSLPhzgy8STdftobKbHoUr6L80v/VpNzjihTwTrXK6FoPV6QNCeiDiwtmw4OOSBOZnM0wqu7uP4SA==; 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charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-Network-Message-Id: 9c0dfb05-2bb6-42c2-edfb-08d6407befd2 X-MS-Exchange-CrossTenant-originalarrivaltime: 02 Nov 2018 04:30:36.7346 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: f34e5979-57d9-4aaa-ad4d-b122a662184d X-MS-Exchange-Transport-CrossTenantHeadersStamped: AM6PR08MB2951 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 04:30:39 -0000 =A0 On Thu, 1 Nov 2018 17:53:51 +0800=20 Gavin Hu wrote:=20 > +* **Updated the ring library with C11 memory model.**=20 > +=20 > + Updated the ring library with C11 memory model including the following = changes:=20 > +=20 > + * Synchronize the load and store of the tail=20 > + * Move the atomic load of head above the loop=20 > +=20 Does this really need to be in the release notes? Is it a user visible chan= ge=20 or just an internal/optimization and fix.=20 [Gavin] There is no api changes, but this is a significant change as ring i= s 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 d= eeper 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 criter= ia to choose between these 2 algorithms. IMO, it probably makes sense to in= dicate that the performance of c11 based algorithm has been improved. Howev= er, 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.