From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bart Van Assche Subject: Re: [PATCH 1/5] block: don't call blk_mq_delay_run_hw_queue() in case of BLK_STS_RESOURCE Date: Tue, 19 Sep 2017 16:49:15 +0000 Message-ID: <1505839754.2671.42.camel@wdc.com> References: <20170915164456.9803-1-ming.lei@redhat.com> <20170915164456.9803-2-ming.lei@redhat.com> <1505498249.3420.15.camel@wdc.com> <20170917124000.GB6289@ming.t460p> <1505747894.2685.6.camel@wdc.com> <20170919054308.GA2517@ming.t460p> <1505835394.2671.18.camel@wdc.com> <20170919155603.GB22809@redhat.com> <20170919160401.GC19830@ming.t460p> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Return-path: In-Reply-To: <20170919160401.GC19830@ming.t460p> Content-Language: en-US Content-ID: <65E0B0232B112440949EED09200096F6@namprd04.prod.outlook.com> Sender: linux-scsi-owner@vger.kernel.org To: "ming.lei@redhat.com" , "snitzer@redhat.com" Cc: "linux-block@vger.kernel.org" , "hch@infradead.org" , "sagi@grimberg.me" , "martin.petersen@oracle.com" , "linux-scsi@vger.kernel.org" , "axboe@fb.com" , "linux-nvme@lists.infradead.org" , "jejb@linux.vnet.ibm.com" , "loberman@redhat.com" , "dm-devel@redhat.com" List-Id: dm-devel.ids T24gV2VkLCAyMDE3LTA5LTIwIGF0IDAwOjA0ICswODAwLCBNaW5nIExlaSB3cm90ZToNCj4gUnVu IHF1ZXVlIGF0IGVuZF9pbyBpcyBkZWZpbml0ZWx5IHdyb25nLCBiZWNhdXNlIGJsay1tcSBoYXMg U0NIRURfUkVTVEFSVA0KPiB0byBkbyB0aGF0IGFscmVhZHkuDQoNClNvcnJ5IGJ1dCBJIGRpc2Fn cmVlLiBJZiBTQ0hFRF9SRVNUQVJUIGlzIHNldCB0aGF0IGNhdXNlcyB0aGUgYmxrLW1xIGNvcmUg dG8NCnJlZXhhbWluZSB0aGUgc29mdHdhcmUgcXVldWVzIGFuZCB0aGUgaGN0eCBkaXNwYXRjaCBs aXN0IGJ1dCBub3QgdGhlIHJlcXVldWUNCmxpc3QuIElmIGEgYmxvY2sgZHJpdmVyIHJldHVybnMg QkxLX1NUU19SRVNPVVJDRSB0aGVuIHJlcXVlc3RzIGVuZCB1cCBvbiB0aGUNCnJlcXVldWUgbGlz dC4gSGVuY2UgdGhlIGZvbGxvd2luZyBjb2RlIGluIHNjc2lfZW5kX3JlcXVlc3QoKToNCg0KCWlm IChzY3NpX3RhcmdldChzZGV2KS0+c2luZ2xlX2x1biB8fCAhbGlzdF9lbXB0eSgmc2Rldi0+aG9z dC0+c3RhcnZlZF9saXN0KSkNCgkJa2Jsb2NrZF9zY2hlZHVsZV93b3JrKCZzZGV2LT5yZXF1ZXVl X3dvcmspOw0KCWVsc2UNCgkJYmxrX21xX3J1bl9od19xdWV1ZXMocSwgdHJ1ZSk7DQoNCkJhcnQu From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from esa1.hgst.iphmx.com ([68.232.141.245]:47117 "EHLO esa1.hgst.iphmx.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750872AbdISQtT (ORCPT ); Tue, 19 Sep 2017 12:49:19 -0400 From: Bart Van Assche To: "ming.lei@redhat.com" , "snitzer@redhat.com" CC: "linux-block@vger.kernel.org" , "hch@infradead.org" , "sagi@grimberg.me" , "martin.petersen@oracle.com" , "linux-scsi@vger.kernel.org" , "axboe@fb.com" , "linux-nvme@lists.infradead.org" , "jejb@linux.vnet.ibm.com" , "loberman@redhat.com" , "dm-devel@redhat.com" Subject: Re: [PATCH 1/5] block: don't call blk_mq_delay_run_hw_queue() in case of BLK_STS_RESOURCE Date: Tue, 19 Sep 2017 16:49:15 +0000 Message-ID: <1505839754.2671.42.camel@wdc.com> References: <20170915164456.9803-1-ming.lei@redhat.com> <20170915164456.9803-2-ming.lei@redhat.com> <1505498249.3420.15.camel@wdc.com> <20170917124000.GB6289@ming.t460p> <1505747894.2685.6.camel@wdc.com> <20170919054308.GA2517@ming.t460p> <1505835394.2671.18.camel@wdc.com> <20170919155603.GB22809@redhat.com> <20170919160401.GC19830@ming.t460p> In-Reply-To: <20170919160401.GC19830@ming.t460p> Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Sender: linux-block-owner@vger.kernel.org List-Id: linux-block@vger.kernel.org T24gV2VkLCAyMDE3LTA5LTIwIGF0IDAwOjA0ICswODAwLCBNaW5nIExlaSB3cm90ZToNCj4gUnVu IHF1ZXVlIGF0IGVuZF9pbyBpcyBkZWZpbml0ZWx5IHdyb25nLCBiZWNhdXNlIGJsay1tcSBoYXMg U0NIRURfUkVTVEFSVA0KPiB0byBkbyB0aGF0IGFscmVhZHkuDQoNClNvcnJ5IGJ1dCBJIGRpc2Fn cmVlLiBJZiBTQ0hFRF9SRVNUQVJUIGlzIHNldCB0aGF0IGNhdXNlcyB0aGUgYmxrLW1xIGNvcmUg dG8NCnJlZXhhbWluZSB0aGUgc29mdHdhcmUgcXVldWVzIGFuZCB0aGUgaGN0eCBkaXNwYXRjaCBs aXN0IGJ1dCBub3QgdGhlIHJlcXVldWUNCmxpc3QuIElmIGEgYmxvY2sgZHJpdmVyIHJldHVybnMg QkxLX1NUU19SRVNPVVJDRSB0aGVuIHJlcXVlc3RzIGVuZCB1cCBvbiB0aGUNCnJlcXVldWUgbGlz dC4gSGVuY2UgdGhlIGZvbGxvd2luZyBjb2RlIGluIHNjc2lfZW5kX3JlcXVlc3QoKToNCg0KCWlm IChzY3NpX3RhcmdldChzZGV2KS0+c2luZ2xlX2x1biB8fCAhbGlzdF9lbXB0eSgmc2Rldi0+aG9z dC0+c3RhcnZlZF9saXN0KSkNCgkJa2Jsb2NrZF9zY2hlZHVsZV93b3JrKCZzZGV2LT5yZXF1ZXVl X3dvcmspOw0KCWVsc2UNCgkJYmxrX21xX3J1bl9od19xdWV1ZXMocSwgdHJ1ZSk7DQoNCkJhcnQu From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bart.VanAssche@wdc.com (Bart Van Assche) Date: Tue, 19 Sep 2017 16:49:15 +0000 Subject: [PATCH 1/5] block: don't call blk_mq_delay_run_hw_queue() in case of BLK_STS_RESOURCE In-Reply-To: <20170919160401.GC19830@ming.t460p> References: <20170915164456.9803-1-ming.lei@redhat.com> <20170915164456.9803-2-ming.lei@redhat.com> <1505498249.3420.15.camel@wdc.com> <20170917124000.GB6289@ming.t460p> <1505747894.2685.6.camel@wdc.com> <20170919054308.GA2517@ming.t460p> <1505835394.2671.18.camel@wdc.com> <20170919155603.GB22809@redhat.com> <20170919160401.GC19830@ming.t460p> Message-ID: <1505839754.2671.42.camel@wdc.com> On Wed, 2017-09-20@00:04 +0800, Ming Lei wrote: > Run queue at end_io is definitely wrong, because blk-mq has SCHED_RESTART > to do that already. Sorry but I disagree. If SCHED_RESTART is set that causes the blk-mq core to reexamine the software queues and the hctx dispatch list but not the requeue list. If a block driver returns BLK_STS_RESOURCE then requests end up on the requeue list. Hence the following code in scsi_end_request(): if (scsi_target(sdev)->single_lun || !list_empty(&sdev->host->starved_list)) kblockd_schedule_work(&sdev->requeue_work); else blk_mq_run_hw_queues(q, true); Bart.