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Tue, 16 Oct 2018 23:26:58 +0000 From: Honnappa Nagarahalli To: "Wang, Yipeng1" , "Richardson, Bruce" , "De Lara Guarch, Pablo" CC: "dev@dpdk.org" , Dharmik Thakkar , "Gavin Hu (Arm Technology China)" , nd , "Gobriel, Sameh" Thread-Topic: [PATCH v3 3/7] hash: correct key store element alignment Thread-Index: AQHUYfVeAJoUIMvE1UaIHWMu8r/gDaUcYSAwgAWXJmA= Date: Tue, 16 Oct 2018 23:26:58 +0000 Message-ID: References: <1539325918-125438-1-git-send-email-honnappa.nagarahalli@arm.com> <1539325918-125438-4-git-send-email-honnappa.nagarahalli@arm.com> 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: [217.140.111.135] x-ms-publictraffictype: Email x-microsoft-exchange-diagnostics: 1; DB7PR08MB3130; 6:tC9la18nhlT15XWeNCgSkACnfrMpAys+c8yH7m7DNVNjnKdHLTRnDaJZiQFGDXznE5PWrs7jm15hFwLwG5jbfO06w0aphU1z4kXRjfZP3WTflkWcR3YJg8jcWauaAbTyFqkvg8B/9uaQPUAbu3Q6SYBb0dzV4Q/xpaVXwsGltb8mYKYRMBumIyKLJmMsmmH5Eua/zZc+TJ4Da41zjv84ZARARvpZqXrkdUpzWg4343JaNqfKwJvOrnz+K6fAoZE3o1DnF4xBUW/X0ADyL1Y/Xi9aiOeMCTwqVlMbDVs1iT+/D83WhDTzQZVU0tT+Abqwwd0m3LRpMWAGa6xxVp6eVbvJDQCkFhCsKzHJEVV5qxDfVMVLmbufhrDlNNu2aZF8psaQSeaD1XXCUHuQjTgQ+05Dgc0IEJ1dT5ChTDWIvclnDWv5qikwpmpJa+k7lQo3RLA0wynX1Xww1PZWyq4EDA==; 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DIR:OUT; SFP:1101; SCL:1; SRVR:DB7PR08MB3130; H:DB7PR08MB3674.eurprd08.prod.outlook.com; FPR:; SPF:None; LANG:en; PTR:InfoNoRecords; MX:1; A:1; received-spf: None (protection.outlook.com: arm.com does not designate permitted sender hosts) x-microsoft-antispam-message-info: 1E3/u5AAJKHl8PRBoPuGdLvH/nV0g0wMZa6XEiENi+FmDzt138nWzmR0t5uitfEjgiqwjz+z8/xJdZmpl/RWDUvsOirKa1g812q6hhHfereYUNpa4ShzW4QtUbKn+dwkf0Swtpz7+tB9lWdf1epFFKYpOQSbPtF4cvMDcjRH/eiG2rqzXxlIKxG342c15eqUHZtIqpP4s7AJtdS/T5xKC4Xq6EuB0D2gH3g+ukPPmrlawn+uiLexna4TB98jiAHi34mFXxorNqsI/YoDeYe42PiqibsLNEAS3hHF1vr4OUOMVAx0/X84ZKHv8RVCg3jQla4C7MGP/bctjfQNa5F/PZLgoZEdZSXJdDriLLINiPk= spamdiagnosticoutput: 1:99 spamdiagnosticmetadata: NSPM Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-Network-Message-Id: 4cb40b49-c9d8-4c7e-4b51-08d633bede21 X-MS-Exchange-CrossTenant-originalarrivaltime: 16 Oct 2018 23:26:58.1719 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: f34e5979-57d9-4aaa-ad4d-b122a662184d X-MS-Exchange-Transport-CrossTenantHeadersStamped: DB7PR08MB3130 Subject: Re: [dpdk-dev] [PATCH v3 3/7] hash: correct key store element alignment X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 16 Oct 2018 23:27:00 -0000 > >-----Original Message----- > >From: Honnappa Nagarahalli [mailto:honnappa.nagarahalli@arm.com] > >Sent: Thursday, October 11, 2018 11:32 PM > >To: Richardson, Bruce ; De Lara Guarch, > >Pablo > >Cc: dev@dpdk.org; Wang, Yipeng1 ; > >honnappa.nagarahalli@arm.com; dharmik.thakkar@arm.com; > >gavin.hu@arm.com; nd@arm.com > >Subject: [PATCH v3 3/7] hash: correct key store element alignment > [Wang, Yipeng] "correct" -> "improve"? I think 'fix' is the right word to use. If we look at the existing code, or= iginal author seems to have tried to align it on certain boundary: struct rte_hash_key { union { uintptr_t idata; void *pdata; }; /* Variable key size */ char key[0]; } __attribute__((aligned(KEY_ALIGNMENT))); But, this does not align every element of the key-store on the alignment bo= undary. This patch fixes it. I think what is missing is the "Fixes" tag. I will add that. I found this bug because I made the store/load of 'pdata' atomic. > > > >Correct the key store array element alignment. This is required to make > >'pdata' in 'struct rte_hash_key' align on the correct boundary. > [Wang, Yipeng] > More explanation in commit message is appreciated, because people may not > understand what is "correct" boundary. > e.g. Previously pdata could spread across multiple cache lines, which mak= es > the access of pdata non-atomic which may have performance implications. >=20 I will add more explanation related to atomic access. > Otherwise > Reviewed-by: Yipeng Wang