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Tue, 10 Dec 2019 00:42:58 +0000 Received: from MN2PR15MB3213.namprd15.prod.outlook.com ([fe80::6d1e:f2f7:d36:a42f]) by MN2PR15MB3213.namprd15.prod.outlook.com ([fe80::6d1e:f2f7:d36:a42f%4]) with mapi id 15.20.2516.018; Tue, 10 Dec 2019 00:42:58 +0000 From: Martin Lau To: Magnus Karlsson CC: "bjorn.topel@intel.com" , "ast@kernel.org" , "daniel@iogearbox.net" , "netdev@vger.kernel.org" , "jonathan.lemon@gmail.com" , "bpf@vger.kernel.org" , "saeedm@mellanox.com" , "jeffrey.t.kirsher@intel.com" , "maciej.fijalkowski@intel.com" , "maciejromanfijalkowski@gmail.com" Subject: Re: [PATCH bpf-next 02/12] xsk: consolidate to one single cached producer pointer Thread-Topic: [PATCH bpf-next 02/12] xsk: consolidate to one single cached producer pointer Thread-Index: AQHVrmZI+YQrK/QS9kuzCSZeM0rJpaeyiLcA Date: Tue, 10 Dec 2019 00:42:58 +0000 Message-ID: <20191210004254.m5cicj3tkc2bhlrd@kafai-mbp> References: <1575878189-31860-1-git-send-email-magnus.karlsson@intel.com> <1575878189-31860-3-git-send-email-magnus.karlsson@intel.com> In-Reply-To: <1575878189-31860-3-git-send-email-magnus.karlsson@intel.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-clientproxiedby: MWHPR1601CA0015.namprd16.prod.outlook.com (2603:10b6:300:da::25) To MN2PR15MB3213.namprd15.prod.outlook.com (2603:10b6:208:3d::12) x-ms-exchange-messagesentrepresentingtype: 1 x-originating-ip: [2620:10d:c090:200::2:ba63] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: 78ba0c1c-0c07-4938-c5f7-08d77d09e70c x-ms-traffictypediagnostic: MN2PR15MB3392: x-microsoft-antispam-prvs: x-ms-oob-tlc-oobclassifiers: OLM:7219; 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charset="us-ascii" Content-ID: <9391CEA730FFB140AC2D472B7AFAA89C@namprd15.prod.outlook.com> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-Network-Message-Id: 78ba0c1c-0c07-4938-c5f7-08d77d09e70c X-MS-Exchange-CrossTenant-originalarrivaltime: 10 Dec 2019 00:42:58.3734 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 8ae927fe-1255-47a7-a2af-5f3a069daaa2 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: V9XF+efLu16IrLmQ73nRru9N3twwgONzNoXDOXKKAY7x4abraV+8Bs2BO5Qvjioc X-MS-Exchange-Transport-CrossTenantHeadersStamped: MN2PR15MB3392 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.95,18.0.572 definitions=2019-12-09_05:2019-12-09,2019-12-09 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 phishscore=0 malwarescore=0 clxscore=1011 adultscore=0 impostorscore=0 lowpriorityscore=0 mlxlogscore=352 suspectscore=0 spamscore=0 priorityscore=1501 bulkscore=0 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-1910280000 definitions=main-1912100004 X-FB-Internal: deliver Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Mon, Dec 09, 2019 at 08:56:19AM +0100, Magnus Karlsson wrote: > Currently, the xsk ring code has two cached producer pointers: > prod_head and prod_tail. This patch consolidates these two into a > single one called cached_prod to make the code simpler and easier to > maintain. This will be in line with the user space part of the the > code found in libbpf, that only uses a single cached pointer. >=20 > The Rx path only uses the two top level functions > xskq_produce_batch_desc and xskq_produce_flush_desc and they both use > prod_head and never prod_tail. So just move them over to > cached_prod. >=20 > The Tx XDP_DRV path uses xskq_produce_addr_lazy and > xskq_produce_flush_addr_n and unnecessarily operates on both prod_tail > and prod_cons, so move them over to just use cached_prod by skipping prod_cons or prod_head? > the intermediate step of updating prod_tail. >=20 > The Tx path in XDP_SKB mode uses xskq_reserve_addr and > xskq_produce_addr. They currently use both cached pointers, but we can > operate on the global producer pointer in xskq_produce_addr since it > has to be updated anyway, thus eliminating the use of both cached > pointers. We can also remove the xskq_nb_free in xskq_produce_addr > since it is already called in xskq_reserve_addr. No need to do it > twice. >=20 > When there is only one cached producer pointer, we can also simplify > xskq_nb_free by removing one argument.