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 23:25:47 +0000 Message-ID: <1505863546.2671.55.camel@wdc.com> References: <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> <1505839754.2671.42.camel@wdc.com> <1505846549.2671.52.camel@wdc.com> <20170919224410.GA21829@ming.t460p> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Return-path: In-Reply-To: <20170919224410.GA21829@ming.t460p> Content-Language: en-US Content-ID: <13C2EA50845865459AF92EAA58C57B5A@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" , "tom.leiming@gmail.com" , "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 T24gV2VkLCAyMDE3LTA5LTIwIGF0IDA2OjQ0ICswODAwLCBNaW5nIExlaSB3cm90ZToNCj4gRm9y IHRoaXMgaXNzdWUsIGl0IGlzbid0IHNhbWUgYmV0d2VlbiBTQ1NJIGFuZCBkbS1ycS4NCj4gDQo+ IFdlIGRvbid0IG5lZWQgdG8gcnVuIHF1ZXVlIGluIC5lbmRfaW8gb2YgZG0sIGFuZCB0aGUgdGhl b3J5IGlzDQo+IHNpbXBsZSwgb3RoZXJ3aXNlIGl0IGlzbid0IHBlcmZvcm1hbmNlIGlzc3VlLCBh bmQgc2hvdWxkIGJlIEkvTyBoYW5nLg0KPiANCj4gMSkgZXZlcnkgZG0tcnEncyByZXF1ZXN0IGlz IDE6MSBtYXBwZWQgdG8gU0NTSSdzIHJlcXVlc3QNCj4gDQo+IDIpIGlmIHRoZXJlIGlzIGFueSBt YXBwZWQgU0NTSSByZXF1ZXN0IG5vdCBmaW5pc2hlZCwgZWl0aGVyDQo+IGluLWZsaWdodCBvciBp biByZXF1ZXVlIGxpc3Qgb3Igd2hhdGV2ZXIsIHRoZXJlIHdpbGwgYmUgb25lDQo+IGNvcnJlc3Bv bmRpbmcgZG0tcnEncyByZXF1ZXN0IGluLWZsaWdodA0KPiANCj4gMykgb25jZSB0aGUgbWFwcGVk IFNDU0kgcmVxdWVzdCBpcyBjb21wbGV0ZWQsIGRtLXJxJ3MgY29tcGxldGlvbg0KPiBwYXRoIHdp bGwgYmUgdHJpZ2dlcmVkIGFuZCBkbS1ycSdzIHF1ZXVlIHdpbGwgYmUgcmVydW4gYmVjYXVzZSBv Zg0KPiBTQ0hFRF9SRVNUQVJUIGluIGRtLXJxDQo+IA0KPiBTbyB0aGUgaHcgcXVldWUgb2YgZG0t cnEgaGFzIGJlZW4gcnVuIGluIGRtLXJxJ3MgY29tcGxldGlvbiBwYXRoDQo+IGFscmVhZHksIHJp Z2h0PyBXaHkgZG8gd2UgbmVlZCB0byBkbyBpdCBhZ2FpbiBpbiB0aGUgaG90IHBhdGg/DQoNClRo ZSBtZWFzdXJlbWVudCBkYXRhIGluIHRoZSBkZXNjcmlwdGlvbiBvZiBwYXRjaCA1LzUgc2hvd3Mg YSBzaWduaWZpY2FudA0KcGVyZm9ybWFuY2UgcmVncmVzc2lvbiBmb3IgYW4gaW1wb3J0YW50IHdv cmtsb2FkLCBuYW1lbHkgcmFuZG9tIEkvTy4NCkFkZGl0aW9uYWxseSwgdGhlIHBlcmZvcm1hbmNl IGltcHJvdmVtZW50IGZvciBzZXF1ZW50aWFsIEkvTyB3YXMgYWNoaWV2ZWQNCmZvciBhbiB1bnJl YWxpc3RpY2FsbHkgbG93IHF1ZXVlIGRlcHRoLiBTb3JyeSBidXQgZ2l2ZW4gdGhlc2UgbWVhc3Vy ZW1lbnQNCnJlc3VsdHMgSSBkb24ndCBzZWUgd2h5IEkgc2hvdWxkIHNwZW5kIG1vcmUgdGltZSBv biB0aGlzIHBhdGNoIHNlcmllcy4NCg0KQmFydC4= From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from esa3.hgst.iphmx.com ([216.71.153.141]:50420 "EHLO esa3.hgst.iphmx.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751237AbdISXZv (ORCPT ); Tue, 19 Sep 2017 19:25:51 -0400 From: Bart Van Assche To: "ming.lei@redhat.com" CC: "linux-block@vger.kernel.org" , "hch@infradead.org" , "tom.leiming@gmail.com" , "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: Tue, 19 Sep 2017 23:25:47 +0000 Message-ID: <1505863546.2671.55.camel@wdc.com> References: <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> <1505839754.2671.42.camel@wdc.com> <1505846549.2671.52.camel@wdc.com> <20170919224410.GA21829@ming.t460p> In-Reply-To: <20170919224410.GA21829@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 T24gV2VkLCAyMDE3LTA5LTIwIGF0IDA2OjQ0ICswODAwLCBNaW5nIExlaSB3cm90ZToNCj4gRm9y IHRoaXMgaXNzdWUsIGl0IGlzbid0IHNhbWUgYmV0d2VlbiBTQ1NJIGFuZCBkbS1ycS4NCj4gDQo+ IFdlIGRvbid0IG5lZWQgdG8gcnVuIHF1ZXVlIGluIC5lbmRfaW8gb2YgZG0sIGFuZCB0aGUgdGhl b3J5IGlzDQo+IHNpbXBsZSwgb3RoZXJ3aXNlIGl0IGlzbid0IHBlcmZvcm1hbmNlIGlzc3VlLCBh bmQgc2hvdWxkIGJlIEkvTyBoYW5nLg0KPiANCj4gMSkgZXZlcnkgZG0tcnEncyByZXF1ZXN0IGlz IDE6MSBtYXBwZWQgdG8gU0NTSSdzIHJlcXVlc3QNCj4gDQo+IDIpIGlmIHRoZXJlIGlzIGFueSBt YXBwZWQgU0NTSSByZXF1ZXN0IG5vdCBmaW5pc2hlZCwgZWl0aGVyDQo+IGluLWZsaWdodCBvciBp biByZXF1ZXVlIGxpc3Qgb3Igd2hhdGV2ZXIsIHRoZXJlIHdpbGwgYmUgb25lDQo+IGNvcnJlc3Bv bmRpbmcgZG0tcnEncyByZXF1ZXN0IGluLWZsaWdodA0KPiANCj4gMykgb25jZSB0aGUgbWFwcGVk IFNDU0kgcmVxdWVzdCBpcyBjb21wbGV0ZWQsIGRtLXJxJ3MgY29tcGxldGlvbg0KPiBwYXRoIHdp bGwgYmUgdHJpZ2dlcmVkIGFuZCBkbS1ycSdzIHF1ZXVlIHdpbGwgYmUgcmVydW4gYmVjYXVzZSBv Zg0KPiBTQ0hFRF9SRVNUQVJUIGluIGRtLXJxDQo+IA0KPiBTbyB0aGUgaHcgcXVldWUgb2YgZG0t cnEgaGFzIGJlZW4gcnVuIGluIGRtLXJxJ3MgY29tcGxldGlvbiBwYXRoDQo+IGFscmVhZHksIHJp Z2h0PyBXaHkgZG8gd2UgbmVlZCB0byBkbyBpdCBhZ2FpbiBpbiB0aGUgaG90IHBhdGg/DQoNClRo ZSBtZWFzdXJlbWVudCBkYXRhIGluIHRoZSBkZXNjcmlwdGlvbiBvZiBwYXRjaCA1LzUgc2hvd3Mg YSBzaWduaWZpY2FudA0KcGVyZm9ybWFuY2UgcmVncmVzc2lvbiBmb3IgYW4gaW1wb3J0YW50IHdv cmtsb2FkLCBuYW1lbHkgcmFuZG9tIEkvTy4NCkFkZGl0aW9uYWxseSwgdGhlIHBlcmZvcm1hbmNl IGltcHJvdmVtZW50IGZvciBzZXF1ZW50aWFsIEkvTyB3YXMgYWNoaWV2ZWQNCmZvciBhbiB1bnJl YWxpc3RpY2FsbHkgbG93IHF1ZXVlIGRlcHRoLiBTb3JyeSBidXQgZ2l2ZW4gdGhlc2UgbWVhc3Vy ZW1lbnQNCnJlc3VsdHMgSSBkb24ndCBzZWUgd2h5IEkgc2hvdWxkIHNwZW5kIG1vcmUgdGltZSBv biB0aGlzIHBhdGNoIHNlcmllcy4NCg0KQmFydC4= From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bart.VanAssche@wdc.com (Bart Van Assche) Date: Tue, 19 Sep 2017 23:25:47 +0000 Subject: [PATCH 1/5] block: don't call blk_mq_delay_run_hw_queue() in case of BLK_STS_RESOURCE In-Reply-To: <20170919224410.GA21829@ming.t460p> References: <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> <1505839754.2671.42.camel@wdc.com> <1505846549.2671.52.camel@wdc.com> <20170919224410.GA21829@ming.t460p> Message-ID: <1505863546.2671.55.camel@wdc.com> On Wed, 2017-09-20@06:44 +0800, Ming Lei wrote: > For this issue, it isn't same between SCSI and dm-rq. > > We don't need to run queue in .end_io of dm, and the theory is > simple, otherwise it isn't performance issue, and should be I/O hang. > > 1) every dm-rq's request is 1:1 mapped to SCSI's request > > 2) if there is any mapped SCSI request not finished, either > in-flight or in requeue list or whatever, there will be one > corresponding dm-rq's request in-flight > > 3) once the mapped SCSI request is completed, dm-rq's completion > path will be triggered and dm-rq's queue will be rerun because of > SCHED_RESTART in dm-rq > > So the hw queue of dm-rq has been run in dm-rq's completion path > already, right? Why do we need to do it again in the hot path? The measurement data in the description of patch 5/5 shows a significant performance regression for an important workload, namely random I/O. Additionally, the performance improvement for sequential I/O was achieved for an unrealistically low queue depth. Sorry but given these measurement results I don't see why I should spend more time on this patch series. Bart.