From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: [PATCH] queue stall with blk-mq-sched To: Jens Axboe References: <762cb508-1de0-93e2-5643-3fe946428eb5@fb.com> <8abc2430-e1fd-bece-ad52-c6d1d482c1e0@suse.de> <1663de5d-cdf7-a6ed-7539-c7d1f5e98f6c@fb.com> <717c595a-a3a6-0508-b537-8cf9e273271e@kernel.dk> <8178340b-dd64-c02d-0ef2-97ad5f928dc8@suse.de> <2b40b443-3bd6-717a-11ba-043886780adf@suse.de> <6035003f-029c-6cff-c35f-4e90496cab50@suse.de> <57539c5d-be3b-ab26-c6d4-a7ff554ded8b@suse.de> <3261ba64-cd7b-a7da-c407-c3b9828c3b57@kernel.dk> <262c4739-be6c-94e9-8e8c-6e97a602e881@kernel.dk> <1447bc07-9336-14f2-8495-a109113050ec@kernel.dk> <4e7abe98-6374-e4d6-5252-42f4fd585e64@suse.de> <5240a94e-56f3-4332-5e4a-4b8d39ba3880@kernel.dk> Cc: "linux-block@vger.kernel.org" , Omar Sandoval From: Hannes Reinecke Message-ID: <94c43936-6f7e-0b4e-c09c-f103e0057711@suse.de> Date: Fri, 27 Jan 2017 07:58:09 +0100 MIME-Version: 1.0 In-Reply-To: <5240a94e-56f3-4332-5e4a-4b8d39ba3880@kernel.dk> Content-Type: text/plain; charset=utf-8 List-ID: On 01/26/2017 05:42 PM, Jens Axboe wrote: > On 01/26/2017 09:35 AM, Hannes Reinecke wrote: >> On 01/25/2017 11:27 PM, Jens Axboe wrote: [ .. ] >>> And another variant, this one should be better in that it should result >>> in less queue runs and get better merging. Hope it works with your >>> stalls as well. >>> >>> >> >> Looking good; queue stalls are gone, and performance is okay-ish. >> I'm getting 84k IOPs now, which is not bad. > > Is that a tested-by? > Not yet; while doing the performance analysis the system now got a queue stalled with _legacy_ SQ. Need to figure out if it's my mpt3sas patches or something else. >> But we absolutely need to work on I/O merging; with CFQ I'm seeing >> requests having about double the size of those done by mq-deadline. >> (Bit unfair, I know :-) >> >> I'll be having some more data in time for LSF/MM. > > I agree, looking at the performance delta, it's all about merging. It's > fairly easy to observe with mq-deadline, as merging rates drop > proportionally to the number of queues configured. But even with 1 queue > with scsi-mq, we're still seeing lower merging rates than !mq + > deadline, for instance. > > I'll look at the merging case, it should not be that hard to bring at > least the single queue case to parity with !mq. I'm actually surprised > it isn't already. > Thanks. Cheers, Hannes -- Dr. Hannes Reinecke Teamlead Storage & Networking hare@suse.de +49 911 74053 688 SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton HRB 21284 (AG Nürnberg)