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Thu, 10 Jun 2021 00:39:25 +0000 From: Damien Le Moal To: Bart Van Assche , Jens Axboe CC: "linux-block@vger.kernel.org" , Christoph Hellwig , Jaegeuk Kim , Hannes Reinecke , Ming Lei , Johannes Thumshirn , Himanshu Madhani Subject: Re: [PATCH 12/14] block/mq-deadline: Add I/O priority support Thread-Topic: [PATCH 12/14] block/mq-deadline: Add I/O priority support Thread-Index: AQHXXLsQrNfwnSgnmUyY0OBm4aL5wQ== Date: Thu, 10 Jun 2021 00:39:25 +0000 Message-ID: References: <20210608230703.19510-1-bvanassche@acm.org> <20210608230703.19510-13-bvanassche@acm.org> <7fa81169-6c94-f7b1-f086-6f2caa775d41@acm.org> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: acm.org; dkim=none (message not signed) header.d=none;acm.org; dmarc=none action=none header.from=wdc.com; x-originating-ip: [129.253.182.60] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: 3a66ea5c-d25a-47bc-9fff-08d92ba832c1 x-ms-traffictypediagnostic: DM5PR0401MB3528: x-ms-exchange-transport-forked: True x-microsoft-antispam-prvs: wdcipoutbound: EOP-TRUE x-ms-oob-tlc-oobclassifiers: OLM:9508; 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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: DM6PR04MB7081.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 3a66ea5c-d25a-47bc-9fff-08d92ba832c1 X-MS-Exchange-CrossTenant-originalarrivaltime: 10 Jun 2021 00:39:25.4939 (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: DiJlmSvTwHjnUvNZBKJZC9hgH4FttRmHstN7sF35n1Lo3AkVXyjyTc1I91MvOL91yxMNXljqSTyNPbFavBoIbA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM5PR0401MB3528 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 2021/06/10 2:25, Bart Van Assche wrote:=0A= > On 6/8/21 10:03 PM, Damien Le Moal wrote:=0A= >> On 2021/06/09 8:07, Bart Van Assche wrote:=0A= >>> struct deadline_data {=0A= >>> /*=0A= >>> * run time data=0A= >>> */=0A= >>> =0A= >>> /*=0A= >>> - * requests (deadline_rq s) are present on both sort_list and fifo_li= st=0A= >>> + * Requests are present on both sort_list[] and fifo_list[][]. The=0A= >>> + * first index of fifo_list[][] is the I/O priority class (DD_*_PRIO)= .=0A= >>> + * The second index is the data direction (rq_data_dir(rq)).=0A= >>> */=0A= >>> struct rb_root sort_list[DD_DIR_COUNT];=0A= >>> - struct list_head fifo_list[DD_DIR_COUNT];=0A= >>> + struct list_head fifo_list[DD_PRIO_COUNT][DD_DIR_COUNT];=0A= >>=0A= >> Would it make sense to pack these 2 into a sub structure ? e.g.:=0A= >>=0A= >> struct deadline_lists {=0A= >> struct rb_root sort_list;=0A= >> struct list_head fifo_list[DD_PRIO_COUNT];=0A= >> };=0A= >>=0A= >> struct deadline_data {=0A= >> ...=0A= >> /*=0A= >> * Requests are present on both sort_list[] and fifo_list[][]. The=0A= >> * first index of fifo_list[][] is the I/O priority class (DD_*_PRIO).= =0A= >> * The second index is the data direction (rq_data_dir(rq)).=0A= >> */=0A= >> struct deadline_lists lists[DD_DIR_COUNT];=0A= > The deadline_fifo_request() function and several other functions=0A= > examine both directions so I think that grouping per direction would=0A= > complicate these functions. Grouping per I/O priority might help to make= =0A= > these functions easier to read. Do you want me to look further into this?= =0A= =0A= If the code is simplified, yes, let's do it ! And Hannes will be happy as t= he=0A= array of arrays will be removed :)=0A= =0A= >>> + struct deadline_data *dd =3D q->elevator->elevator_data;=0A= >>> + const u8 ioprio_class =3D dd_rq_ioclass(next);=0A= >>> + const enum dd_prio prio =3D ioprio_class_to_prio[ioprio_class];=0A= >>> +=0A= >>> + if (next->elv.priv[0]) {=0A= >>> + dd_count(dd, merged, prio);=0A= >>> + } else {=0A= >>> + WARN_ON_ONCE(true);=0A= >>> + }=0A= >>=0A= >> No need for the curly brackets I think.=0A= > =0A= > I can leave these out but you may want to know that leaving the curly=0A= > brackets out from this patch will make it necessary to introduce these=0A= > in the next patch in this series.=0A= > =0A= >>> +/* Number of requests queued for a given priority level. */=0A= >>> +static u32 dd_queued(struct deadline_data *dd, enum dd_prio prio)=0A= >>> +{=0A= >>> + return dd_sum(dd, inserted, prio) - dd_sum(dd, completed, prio);=0A= >>=0A= >> This also includes requests that are being executed on the device. Is th= at OK ?=0A= > =0A= > Yes, and that's on purpose. Please note that this function is only used= =0A= > to export statistics to user space.=0A= =0A= Yes, I got it that it is only for stats shown to the user. I am just wonder= ing=0A= if we need to separate in-flight requests and queued requests. That should = be=0A= easy to do since you also have the dispatched count.=0A= But again, not entirely sure if it is useful to have such level of detail. = So I=0A= guess it is OK as is for now. We can revisit later if needed.=0A= =0A= > =0A= > Thanks,=0A= > =0A= > Bart.=0A= > =0A= =0A= =0A= -- =0A= Damien Le Moal=0A= Western Digital Research=0A=