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: Mon, 18 Sep 2017 15:18:16 +0000 Message-ID: <1505747894.2685.6.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> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Return-path: In-Reply-To: <20170917124000.GB6289@ming.t460p> Content-Language: en-US Content-ID: <2BEB1493B7CA53418C317D2CFF8AE3E0@namprd04.prod.outlook.com> Sender: linux-scsi-owner@vger.kernel.org To: "ming.lei@redhat.com" Cc: "linux-block@vger.kernel.org" , "hch@infradead.org" , "sagi@grimberg.me" , "snitzer@redhat.com" , "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 T24gU3VuLCAyMDE3LTA5LTE3IGF0IDIwOjQwICswODAwLCBNaW5nIExlaSB3cm90ZToNCj4gImlm IG5vIHJlcXVlc3QgaGFzIGNvbXBsZXRlZCBiZWZvcmUgdGhlIGRlbGF5IGhhcyBleHBpcmVkIiBj YW4ndCBiZSBhDQo+IHJlYXNvbiB0byByZXJ1biB0aGUgcXVldWUsIGJlY2F1c2UgdGhlIHF1ZXVl IGNhbiBzdGlsbCBiZSBidXN5Lg0KDQpUaGF0IHN0YXRlbWVudCBvZiB5b3Ugc2hvd3MgdGhhdCB0 aGVyZSBhcmUgaW1wb3J0YW50IGFzcGVjdHMgb2YgdGhlIFNDU0kNCmNvcmUgYW5kIGRtLW1wYXRo IGRyaXZlciB0aGF0IHlvdSBkb24ndCB1bmRlcnN0YW5kLg0KDQo+IEkgc3VnZ2VzdCB0byB1bmRl cnN0YW5kIHRoZSByb290IGNhdXNlLCBpbnN0ZWFkIG9mIGtlZXBpbmcgdGhpcw0KPiB1Z2x5IHJh bmRvbSBkZWxheSBiZWNhdXNlIHJ1biBodyBxdWV1ZSBhZnRlciAxMDBtcyBtYXkgYmUgdXNlbGVz cw0KPiBpbiA5OS45OSUgdGltZXMuDQoNCklmIHlvdSBhcmUgc3RpbGwgbG9va2luZyBhdCByZW1v dmluZyB0aGUgYmxrX21xX2RlbGF5X3J1bl9od19xdWV1ZSgpIGNhbGxzDQp0aGVuIEkgdGhpbmsg eW91IGFyZSBsb29raW5nIGluIHRoZSB3cm9uZyBkaXJlY3Rpb24uIFdoYXQga2luZCBvZiBwcm9i bGVtDQphcmUgeW91IHRyeWluZyB0byBzb2x2ZT8gSXMgaXQgcGVyaGFwcyB0aGF0IHRoZXJlIGNh biBiZSBhIGRlbGF5IGJldHdlZW4NCmRtLW1wYXRoIHJlcXVlc3QgY29tcGxldGlvbiBhbmQgdGhl IHF1ZXVlaW5nIG9mIGEgbmV3IHJlcXVlc3Q/IElmIHNvLA0KYWRkaW5nIGEgcXVldWUgcnVuIGNh bGwgaW50byB0aGUgZG0tbXBhdGggZW5kX2lvIGNhbGxiYWNrIGlzIHByb2JhYmx5DQpzdWZmaWNp ZW50IGFuZCBwcm9iYWJseSBjYW4gcmVwbGFjZSB0aGlzIGVudGlyZSBwYXRjaCBzZXJpZXMuDQoN CkJhcnQu From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from esa4.hgst.iphmx.com ([216.71.154.42]:23097 "EHLO esa4.hgst.iphmx.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751416AbdIRPST (ORCPT ); Mon, 18 Sep 2017 11:18:19 -0400 From: Bart Van Assche To: "ming.lei@redhat.com" CC: "linux-block@vger.kernel.org" , "hch@infradead.org" , "sagi@grimberg.me" , "snitzer@redhat.com" , "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: Mon, 18 Sep 2017 15:18:16 +0000 Message-ID: <1505747894.2685.6.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> In-Reply-To: <20170917124000.GB6289@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 T24gU3VuLCAyMDE3LTA5LTE3IGF0IDIwOjQwICswODAwLCBNaW5nIExlaSB3cm90ZToNCj4gImlm IG5vIHJlcXVlc3QgaGFzIGNvbXBsZXRlZCBiZWZvcmUgdGhlIGRlbGF5IGhhcyBleHBpcmVkIiBj YW4ndCBiZSBhDQo+IHJlYXNvbiB0byByZXJ1biB0aGUgcXVldWUsIGJlY2F1c2UgdGhlIHF1ZXVl IGNhbiBzdGlsbCBiZSBidXN5Lg0KDQpUaGF0IHN0YXRlbWVudCBvZiB5b3Ugc2hvd3MgdGhhdCB0 aGVyZSBhcmUgaW1wb3J0YW50IGFzcGVjdHMgb2YgdGhlIFNDU0kNCmNvcmUgYW5kIGRtLW1wYXRo IGRyaXZlciB0aGF0IHlvdSBkb24ndCB1bmRlcnN0YW5kLg0KDQo+IEkgc3VnZ2VzdCB0byB1bmRl cnN0YW5kIHRoZSByb290IGNhdXNlLCBpbnN0ZWFkIG9mIGtlZXBpbmcgdGhpcw0KPiB1Z2x5IHJh bmRvbSBkZWxheSBiZWNhdXNlIHJ1biBodyBxdWV1ZSBhZnRlciAxMDBtcyBtYXkgYmUgdXNlbGVz cw0KPiBpbiA5OS45OSUgdGltZXMuDQoNCklmIHlvdSBhcmUgc3RpbGwgbG9va2luZyBhdCByZW1v dmluZyB0aGUgYmxrX21xX2RlbGF5X3J1bl9od19xdWV1ZSgpIGNhbGxzDQp0aGVuIEkgdGhpbmsg eW91IGFyZSBsb29raW5nIGluIHRoZSB3cm9uZyBkaXJlY3Rpb24uIFdoYXQga2luZCBvZiBwcm9i bGVtDQphcmUgeW91IHRyeWluZyB0byBzb2x2ZT8gSXMgaXQgcGVyaGFwcyB0aGF0IHRoZXJlIGNh biBiZSBhIGRlbGF5IGJldHdlZW4NCmRtLW1wYXRoIHJlcXVlc3QgY29tcGxldGlvbiBhbmQgdGhl IHF1ZXVlaW5nIG9mIGEgbmV3IHJlcXVlc3Q/IElmIHNvLA0KYWRkaW5nIGEgcXVldWUgcnVuIGNh bGwgaW50byB0aGUgZG0tbXBhdGggZW5kX2lvIGNhbGxiYWNrIGlzIHByb2JhYmx5DQpzdWZmaWNp ZW50IGFuZCBwcm9iYWJseSBjYW4gcmVwbGFjZSB0aGlzIGVudGlyZSBwYXRjaCBzZXJpZXMuDQoN CkJhcnQu From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bart.VanAssche@wdc.com (Bart Van Assche) Date: Mon, 18 Sep 2017 15:18:16 +0000 Subject: [PATCH 1/5] block: don't call blk_mq_delay_run_hw_queue() in case of BLK_STS_RESOURCE In-Reply-To: <20170917124000.GB6289@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> Message-ID: <1505747894.2685.6.camel@wdc.com> On Sun, 2017-09-17@20:40 +0800, Ming Lei wrote: > "if no request has completed before the delay has expired" can't be a > reason to rerun the queue, because the queue can still be busy. That statement of you shows that there are important aspects of the SCSI core and dm-mpath driver that you don't understand. > I suggest to understand the root cause, instead of keeping this > ugly random delay because run hw queue after 100ms may be useless > in 99.99% times. If you are still looking at removing the blk_mq_delay_run_hw_queue() calls then I think you are looking in the wrong direction. What kind of problem are you trying to solve? Is it perhaps that there can be a delay between dm-mpath request completion and the queueing of a new request? If so, adding a queue run call into the dm-mpath end_io callback is probably sufficient and probably can replace this entire patch series. Bart.