From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752563AbdJMRI6 (ORCPT ); Fri, 13 Oct 2017 13:08:58 -0400 Received: from esa6.hgst.iphmx.com ([216.71.154.45]:19705 "EHLO esa6.hgst.iphmx.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751633AbdJMRIz (ORCPT ); Fri, 13 Oct 2017 13:08:55 -0400 X-IronPort-AV: E=Sophos;i="5.43,371,1503331200"; d="scan'208";a="58231517" From: Bart Van Assche To: "ming.lei@redhat.com" CC: "linux-kernel@vger.kernel.org" , "linux-block@vger.kernel.org" , "hch@infradead.org" , "tom81094@gmail.com" , "himanshu.madhani@cavium.com" , "paolo.valente@linaro.org" , "axboe@kernel.dk" , "linux-scsi@vger.kernel.org" , "oleksandr@natalenko.name" , "john.garry@huawei.com" , "osandov@fb.com" , "loberman@redhat.com" , "james.smart@broadcom.com" Subject: Re: [PATCH V7 4/6] blk-mq: introduce .get_budget and .put_budget in blk_mq_ops Thread-Topic: [PATCH V7 4/6] blk-mq: introduce .get_budget and .put_budget in blk_mq_ops Thread-Index: AQHTQ4lc2pZDXOhe5U6IuYSs5ux9RaLgjbsAgABdCgCAAPGtgIAAF0GAgAAGiACAAAQCAIAABo2A Date: Fri, 13 Oct 2017 17:08:52 +0000 Message-ID: <1507914527.13345.17.camel@wdc.com> References: <20171012183704.22326-1-ming.lei@redhat.com> <20171012183704.22326-5-ming.lei@redhat.com> <9a741c03-90a3-e583-ddde-0ed71c8570a2@kernel.dk> <20171013001919.GA24715@ming.t460p> <6efdb459-8746-562d-06dc-5b3e172076e1@kernel.dk> <20171013160731.GA30899@ming.t460p> <1507912260.13345.0.camel@wdc.com> <20171013164519.GF30899@ming.t460p> In-Reply-To: <20171013164519.GF30899@ming.t460p> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: spf=none (sender IP is ) smtp.mailfrom=Bart.VanAssche@wdc.com; x-originating-ip: [63.163.107.201] x-ms-publictraffictype: Email x-microsoft-exchange-diagnostics: 1;CY1PR0401MB1535;20:LfNtMKAZuxHJNgED13DAsP8iknRtWLZmk0NYy1m+iCtqF1dNMDKT93DlsBpQjwPMPLYRFkIJVM2LPR9JWRK7fJrxP6tV/S6bC50Urqs1+3DKgM6ZPpXWwAAMEnGIBXaEnkt75xwzOIPHxcpmoXpo875hxlwwMiL19RdqXBeTvLU= x-ms-exchange-antispam-srfa-diagnostics: SSOS; x-ms-office365-filtering-correlation-id: 7c377209-bd9e-4770-996c-08d5125d1463 x-ms-office365-filtering-ht: Tenant x-microsoft-antispam: UriScan:;BCL:0;PCL:0;RULEID:(22001)(2017030254152)(48565401081)(2017052603199)(201703131423075)(201703031133081)(201702281549075);SRVR:CY1PR0401MB1535; x-ms-traffictypediagnostic: CY1PR0401MB1535: wdcipoutbound: EOP-TRUE x-exchange-antispam-report-test: UriScan:; x-microsoft-antispam-prvs: x-exchange-antispam-report-cfa-test: BCL:0;PCL:0;RULEID:(100000700101)(100105000095)(100000701101)(100105300095)(100000702101)(100105100095)(6040450)(2401047)(5005006)(8121501046)(100000703101)(100105400095)(10201501046)(3002001)(93006095)(93001095)(6055026)(6041248)(20161123564025)(20161123562025)(20161123558100)(20161123560025)(201703131423075)(201702281528075)(201703061421075)(201703061406153)(20161123555025)(6072148)(201708071742011)(100000704101)(100105200095)(100000705101)(100105500095);SRVR:CY1PR0401MB1535;BCL:0;PCL:0;RULEID:(100000800101)(100110000095)(100000801101)(100110300095)(100000802101)(100110100095)(100000803101)(100110400095)(100000804101)(100110200095)(100000805101)(100110500095);SRVR:CY1PR0401MB1535; x-forefront-prvs: 04599F3534 x-forefront-antispam-report: SFV:NSPM;SFS:(10019020)(6009001)(376002)(39860400002)(346002)(377424004)(24454002)(189002)(51444003)(199003)(7416002)(5660300001)(2351001)(53936002)(6512007)(2501003)(99286003)(2906002)(81166006)(72206003)(101416001)(305945005)(5640700003)(25786009)(2900100001)(6246003)(36756003)(14454004)(54906003)(33646002)(6916009)(93886005)(86362001)(4001150100001)(316002)(189998001)(81156014)(77096006)(3846002)(229853002)(6486002)(8676002)(6116002)(102836003)(66066001)(106356001)(478600001)(3280700002)(105586002)(8936002)(2950100002)(68736007)(50986999)(3660700001)(6436002)(97736004)(39060400002)(4326008)(7736002)(54356999)(6506006)(103116003)(76176999)(142923001);DIR:OUT;SFP:1102;SCL:1;SRVR:CY1PR0401MB1535;H:CY1PR0401MB1536.namprd04.prod.outlook.com;FPR:;SPF:None;PTR:InfoNoRecords;MX:1;A:1;LANG:en; spamdiagnosticoutput: 1:99 spamdiagnosticmetadata: NSPM Content-Type: text/plain; charset="utf-8" Content-ID: <37B5F4E9924F7E46BBAEF13697FC56A3@namprd04.prod.outlook.com> MIME-Version: 1.0 X-OriginatorOrg: wdc.com X-MS-Exchange-CrossTenant-originalarrivaltime: 13 Oct 2017 17:08:52.4404 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: b61c8803-16f3-4c35-9b17-6f65f441df86 X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY1PR0401MB1535 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from base64 to 8bit by nfs id v9DH93PV019325 On Sat, 2017-10-14 at 00:45 +0800, Ming Lei wrote: > On Fri, Oct 13, 2017 at 04:31:04PM +0000, Bart Van Assche wrote: > > On Sat, 2017-10-14 at 00:07 +0800, Ming Lei wrote: > > > Actually it is in hot path, for example, lpfc and qla2xx's queue depth is 3, > > > > Sorry but I doubt whether that is correct. More in general, I don't know any modern > > storage HBA for which the default queue depth is so low. > > You can grep: > > [ming@ming linux]$ git grep -n cmd_per_lun ./drivers/scsi/ | grep -E "qla2xxx|lpfc" Such a low queue depth will result in suboptimal performance for adapters that communicate over a storage network. I think that's a bug and that both adapters support much higher cmd_per_lun values. (+James Smart) James, can you explain us why commit 445cf4f4d2aa decreased LPFC_CMD_PER_LUN from 30 to 3? Was that perhaps a workaround for a bug in a specific target implementation? (+Himanshu Madhani) Himanshu, do you perhaps know whether it is safe to increase cmd_per_lun for the qla2xxx initiator driver to the scsi_host->can_queue value? > Even SRP/IB isn't big too, just 32. The default value for ib_srp for cmd_per_lun is 62 but that value can be overridden by selecting another value in /etc/default/srp_daemon.conf. Note: a lower value is selected if after SRP login it becomes clear that the target queue depth is lower than the cmd_per_lun value requested by the user. This is a performance optimization and avoids that the SRP target system has to send back BUSY responses to the initiator. Bart.