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Miller" , Jakub Kicinski , "netdev@vger.kernel.org" , Dmitry Bogdanov Subject: Re: [PATCH v4] aquantia: Remove the build_skb path Thread-Topic: [PATCH v4] aquantia: Remove the build_skb path Thread-Index: AQHWvs8ZM2n6oge2KEC89hbATIw5VanQJ1WAgAAAZVA= Date: Fri, 20 Nov 2020 00:23:04 +0000 Message-ID: References: <20201119221510.GI15137@breakpoint.cc> <20201119222800.GJ15137@breakpoint.cc> <20201119225842.GK15137@breakpoint.cc> ,<20201120001705.GL15137@breakpoint.cc> In-Reply-To: <20201120001705.GL15137@breakpoint.cc> Accept-Language: en-AU, en-US Content-Language: en-AU X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: strlen.de; dkim=none (message not signed) header.d=none;strlen.de; dmarc=none action=none header.from=digi.com; x-originating-ip: [158.140.192.185] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: 9660f55f-e09e-4512-13d3-08d88cea72cd x-ms-traffictypediagnostic: CY4PR1001MB2165: x-microsoft-antispam-prvs: x-ms-oob-tlc-oobclassifiers: OLM:10000; x-ms-exchange-senderadcheck: 1 x-microsoft-antispam: BCL:0; x-microsoft-antispam-message-info: 9s2J4aa7rUTZNf/kxW3M29jfUx1j1PEKdkWicOl6XgWtZv6HMZxJlZw8n3DwNGLzfzfRrtw+QNDuosafD0daQUou9iPa5UjTgnDMHMi6HRPLFqEw7NmqTv7Warzm4pQlFbA33N9wfiXuImL3x/kvWUGcRGKmeSRyx1F9c9ugcjHYp2UYtI4tIlIjI6jJN4QwG3Owgu5dyY/nLM0oBWmyFCOou/B8ezVJizNiirrmO/tnu2jXy3jNGfowPBBqTeDOkUKDb/GE7yZBGlpm9+scKpErv1En32R+JEB6p+0dqLlZnAZ1IFBc7WHo83iELJMY x-forefront-antispam-report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:CY4PR1001MB2311.namprd10.prod.outlook.com;PTR:;CAT:NONE;SFS:(4636009)(366004)(376002)(346002)(396003)(39850400004)(136003)(33656002)(478600001)(7696005)(52536014)(4744005)(26005)(2906002)(316002)(86362001)(71200400001)(5660300002)(6506007)(4326008)(6916009)(66946007)(55016002)(186003)(8676002)(54906003)(83380400001)(9686003)(76116006)(66476007)(66556008)(8936002)(64756008)(66446008)(91956017);DIR:OUT;SFP:1102; x-ms-exchange-antispam-messagedata: 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 x-ms-exchange-transport-forked: True Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: digi.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: CY4PR1001MB2311.namprd10.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 9660f55f-e09e-4512-13d3-08d88cea72cd X-MS-Exchange-CrossTenant-originalarrivaltime: 20 Nov 2020 00:23:04.7714 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: abb4cdb7-1b7e-483e-a143-7ebfd1184b9e X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: eYldraHXGfGfTmcnvP88i0hgP8dNJw82I6BobwZi+2ejoappvw0LV+/PXNJNTxvUvcnx5+xzE7h6YXVylnjmRw== X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY4PR1001MB2165 X-BESS-ID: 1605831785-893006-2617-503-1 X-BESS-VER: 2019.1_20201120.0004 X-BESS-Apparent-Source-IP: 104.47.56.173 X-BESS-Outbound-Spam-Score: 0.00 X-BESS-Outbound-Spam-Report: Code version 3.2, rules version 3.2.2.228307 [from cloudscan11-131.us-east-2a.ess.aws.cudaops.com] Rule breakdown below pts rule name description ---- ---------------------- -------------------------------- 0.00 BSF_BESS_OUTBOUND META: BESS Outbound X-BESS-Outbound-Spam-Status: SCORE=0.00 using account:ESS112744 scores of KILL_LEVEL=7.0 tests=BSF_BESS_OUTBOUND X-BESS-BRTS-Status: 1 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org > > I don't know about benefits/feasibility, but I did wonder if (in the ev= ent that the "fast path" is possible), the dma_mapping could use an offset?= The page would include the skb header but the dma mapping would not. If th= at was done though, only 1 RX frame would fit into the page (at least on my= system, where the RX frame seems to be 2k and the page is 4k). Also, there= 's a possibility to set the "order" variable, so that multiple pages are cr= eated at once and I'm not sure if this would work in that case.=0A= > =0A= > Yes, this is what some drivers do, they allocate a page, pass=0A= > pageaddr + headroom_offset everywhere, except build_skb() which gets the= =0A= > pageaddr followed by skb_reserve(skb, headroom_offset).=0A= =0A= If everyone's happy with the patch as-is, I might just leave it and let peo= ple more knowledgeable decide if it's worth adding this optimization back i= n with this offset logic ;)=0A= =0A= Lincoln=0A=