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Bottomley" , Matthias Brugger Subject: RE: [PATCH v2] scsi: ufs: Increase the maximum data buffer size Thread-Topic: [PATCH v2] scsi: ufs: Increase the maximum data buffer size Thread-Index: AQHYoEz6xQdLmdWmM0q7DVw+WscoBa2QmMTA Date: Tue, 26 Jul 2022 12:54:02 +0000 Message-ID: References: <20220725173528.849643-1-bvanassche@acm.org> In-Reply-To: <20220725173528.849643-1-bvanassche@acm.org> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=wdc.com; x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: 9414cd17-043e-4bc3-8c8a-08da6f05ea88 x-ms-traffictypediagnostic: SN6PR04MB4109:EE_ wdcipoutbound: EOP-TRUE x-ms-exchange-senderadcheck: 1 x-ms-exchange-antispam-relay: 0 x-microsoft-antispam: BCL:0; x-microsoft-antispam-message-info: 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 x-forefront-antispam-report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:DM6PR04MB6575.namprd04.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230016)(4636009)(346002)(39860400002)(366004)(376002)(396003)(136003)(6506007)(7696005)(9686003)(478600001)(316002)(8936002)(52536014)(33656002)(5660300002)(186003)(55016003)(41300700001)(82960400001)(86362001)(71200400001)(83380400001)(38100700002)(2906002)(122000001)(38070700005)(4326008)(8676002)(64756008)(66446008)(76116006)(66556008)(66946007)(66476007)(54906003)(26005)(110136005);DIR:OUT;SFP:1102; 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charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: wdc.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: DM6PR04MB6575.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 9414cd17-043e-4bc3-8c8a-08da6f05ea88 X-MS-Exchange-CrossTenant-originalarrivaltime: 26 Jul 2022 12:54:02.6527 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: b61c8803-16f3-4c35-9b17-6f65f441df86 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: C17DLyWbjntfG0lTsJRxyePNc3W24Vj47677Z4bPYXgxjTWMrvb7NNjI2QouYEO5AWc2rP+aKVO4wQnCEcevtg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: SN6PR04MB4109 Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org Bart hi, > Measurements have shown that for some UFS devices the maximum sequential > I/O throughput is achieved with a transfer size above 512 KiB. Hence > increase the maximum size of the data buffer associated with a single > request from SCSI_DEFAULT_MAX_SECTORS (1024) * 512 bytes =3D 512 KiB into > 255 MiB. >=20 > Notes: > - The maximum data buffer size supported by the UFSHCI specification > is 65535 * 256 KiB or about 16 GiB. > - The maximum data buffer size for READ(10) commands is 65535 logical > blocks. To transfer more than 65535 * 4096 bytes =3D 255 MiB with a > single SCSI command, the READ(16) command is required. Support for > READ(16) is optional in the UFS 3.1 and UFS 4.0 standards. I still have concerns of a negative impact of a too-large-max-sectors. I replicate your fio measurements using galaxy S22 - one of the most advanc= ed production platform currently in the market. See the results below: fio bs vs max-sectors. data is the read BW[MiB/s]. Given that: a) there isn't that much of a difference among the various max-sectors b) max-sectors is configurable via max_sectors_kb sysfs entry, and c) going from the benchmark world into the real world, a large write (255Mi= B), interleaved by many small reads (4k), may cause high latency, up to eve= n a timeout (!?) I would leave the max-sectors threshold as it is, or use the moderate 1MB l= imit. Unless you can back the "Measurements have shown" statement with a more co= ncrete data. Thanks, Avri | 1MB | 2MB | 128MB | 255MB ---------------------------------------------------------------------------= ----------------------------------------- 4KiB | 14.7 | 13.3 | 15.7 | 19.5 8KiB | 26.7 | 27.4 | 25.8 | 30.0 16KiB | 44 | 53.2 | 46.3 | 61.2 64KiB | 179 | 207 | 171 | 184 32KiB | 100 | 120 | 105 | 119 128KiB | 275 | 322 | 271 | 256 256KiB | 440 | 452 | 417 | 378 512KiB | 535 | 525 | 483 | 471 1MiB | 592 | 584 | 531 | 408 2MiB | 349 | 361 | 375 | 297 4MiB | 502 | 492 | 515 | 441 8MiB | 645 | 663 | 682 | 650 16MiB | 752 | 749 | 752 | 762 32MiB | 817 | 790 | 822 | 791 64MiB | 1710 | 1703 | 1700 | 1692 128MiB | 1733 | 1730 | 1724 | 1712 256MiB | 1752 | 1748 | 1738 | 1732