From mboxrd@z Thu Jan 1 00:00:00 1970 From: John Garry Subject: Re: [PATCH] scsi: default to scsi-mq Date: Wed, 12 Jul 2017 09:26:04 +0100 Message-ID: <581a258d-3da8-5b01-f528-0ce11b74b65e@huawei.com> References: <20170616082755.22832-1-hch@lst.de> <1499701840.3555.7.camel@wdc.com> <1499779970.3345.1.camel@wdc.com> <4cf7ed21-7cf4-a91a-8beb-ba5f92e4eaaf@huawei.com> <1499788012.2586.12.camel@wdc.com> <9c0db5bd-a623-c73e-9f44-a4cfad97e2c8@huawei.com> Mime-Version: 1.0 Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from szxga03-in.huawei.com ([45.249.212.189]:8897 "EHLO szxga03-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933243AbdGLI1B (ORCPT ); Wed, 12 Jul 2017 04:27:01 -0400 In-Reply-To: <9c0db5bd-a623-c73e-9f44-a4cfad97e2c8@huawei.com> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Bart Van Assche , "hch@lst.de" , "linux-scsi@vger.kernel.org" , "linuxarm@huawei.com" >> What block driver controls the block device for which the performance >> regression >> has been observed? How many hardware queues were created by that block >> driver >> (see also /sys/block/*/mq/...)? > Just confirming that we have only 1 queue: /sys/block/sdc/mq/0 as example > Hi Bart, > > Here's the shost init for our SCSI LLDD: > http://elixir.free-electrons.com/linux/latest/source/drivers/scsi/hisi_sas/hisi_sas_main.c#L1736 > > > So we don't set hr_hw_queues (which would mean = 0), so this should set > shost->tag_set.nr_hw_queues to 1 in scsi_mq_setup_tags(). > > FWIW, I can confirm sysfs entry when I get hw access tomorrow. > > John > > I'm asking this because the number of hardware >> queues controls which I/O scheduler is selected as default. From >> block/elevator.c: >> > > > >> if (q->mq_ops) { >> if (q->nr_hw_queues == 1) >> e = elevator_get("mq-deadline", false); >> if (!e) >> return 0; >> } else >> e = elevator_get(CONFIG_DEFAULT_IOSCHED, false); >> >> Bart. >> > > > _______________________________________________ > linuxarm mailing list > linuxarm@huawei.com > http://rnd-openeuler.huawei.com/mailman/listinfo/linuxarm > > . >