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Wed, 19 May 2021 15:32:49 +0000 From: Johannes Thumshirn To: "dsterba@suse.cz" CC: David Sterba , "linux-btrfs@vger.kernel.org" Subject: Re: [PATCH] btrfs: scrub: per-device bandwidth control Thread-Topic: [PATCH] btrfs: scrub: per-device bandwidth control Thread-Index: AQHXS/Vlei4t9RXqlEKyfFBHrG12jw== Date: Wed, 19 May 2021 15:32:48 +0000 Message-ID: References: <20210518144935.15835-1-dsterba@suse.com> <20210519142612.GW7604@twin.jikos.cz> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: suse.cz; dkim=none (message not signed) header.d=none;suse.cz; dmarc=none action=none header.from=wdc.com; x-originating-ip: [2001:a62:152f:cc01:95b:718f:422f:1ec2] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: 7bd29082-b158-4086-a98c-08d91adb5bea x-ms-traffictypediagnostic: PH0PR04MB7301: x-microsoft-antispam-prvs: wdcipoutbound: EOP-TRUE x-ms-oob-tlc-oobclassifiers: OLM:8882; x-ms-exchange-senderadcheck: 1 x-microsoft-antispam: BCL:0; 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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: PH0PR04MB7416.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 7bd29082-b158-4086-a98c-08d91adb5bea X-MS-Exchange-CrossTenant-originalarrivaltime: 19 May 2021 15:32:48.9929 (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: BU7mFt5gW/CWoXh2s72YisJzXWvfSYuU9i17VdGyKRfgoqA885aXloxjmTG6E7gxup+giN2LKaOPqcdfQYEKPo6WvyLFddKTe1MUetnnwD0= X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH0PR04MB7301 Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On 19/05/2021 16:28, David Sterba wrote:=0A= > On Wed, May 19, 2021 at 06:53:54AM +0000, Johannes Thumshirn wrote:=0A= >> On 18/05/2021 16:52, David Sterba wrote:=0A= >> I wonder if this interface would make sense for limiting balance=0A= >> bandwidth as well?=0A= > =0A= > Balance is not contained to one device, so this makes the scrub case=0A= > easy. For balance there are data and metadata involved, both read and=0A= > write accross several threads so this is really something that the=0A= > cgroups io controler is supposed to do.=0A= > =0A= =0A= For a user initiated balance a cgroups io controller would work well, yes.= =0A= But for having a QoS mechanism to decide when it's a good time to rebalance= =0A= one or more block groups, i.e. with a zoned file system or when we switch= =0A= to auto-balance in the future I'm not sure if cgroups would help us much=0A= in this case.=0A= =0A= But this can be my lack of knowledge as well.=0A=