From mboxrd@z Thu Jan 1 00:00:00 1970 From: James Bottomley Subject: Re: [Lsf] [LSF/MM TOPIC] block-mq issues with FC Date: Fri, 08 Apr 2016 11:24:08 -0700 Message-ID: <1460139848.2340.62.camel@HansenPartnership.com> References: <57079616.4000202@suse.de> <20160408174006.GI2781@linux.intel.com> <1460138451.2340.60.camel@HansenPartnership.com> <20160408180832.GA22340@lst.de> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: Received: from bedivere.hansenpartnership.com ([66.63.167.143]:35188 "EHLO bedivere.hansenpartnership.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753056AbcDHSYL (ORCPT ); Fri, 8 Apr 2016 14:24:11 -0400 In-Reply-To: <20160408180832.GA22340@lst.de> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Christoph Hellwig Cc: Jens Axboe , "linux-block@vger.kernel.org" , SCSI Mailing List , lsf@lists.linux-foundation.org, Hannes Reinecke , Matthew Wilcox On Fri, 2016-04-08 at 20:08 +0200, Christoph Hellwig wrote: > On Fri, Apr 08, 2016 at 11:00:51AM -0700, James Bottomley wrote: > > > - Inability to use all queues supported by a device. Intel's > > > P3700 > > > supports 31 queues, but block-mq insists on assigning an even > > > multiple > > > of CPUs to each queue. So if you have 48 CPUs, it will use 24 > > > queues. > > > If you have 128 CPUs, it will only use 16 of the queues. > > > > > > - Interrupt steering needs to be controlled by block-mq instead > > > of > > > the driver. It's pointless to have each driver implement its > > > own > > > policies on interrupt steering, irqbalanced remains a source > > > of > > > end-user frustration, and block-mq can change the queue<->cpu > > > mapping > > > without the driver's knowledge. > > > > > > (thanks to Keith for his input on the first and suggestion of the > > > second). > > > > OK, what about two sessions, one for general bitching (the feedback > > sessions) and one for concrete proposals for improvements ... so > > rather > > than just complaining about the problem, if you have concrete ideas > > about fixing it, that would go into the second session. > > We already have the blk-mq interrupt assignment session on the > schedule, > which is about willy's item. And my work in progress code to address > the issue also mostly addresses his item number 1, so I think we can > just keep the schedule most as is and just rename "multiqueue > interrupt > assignment" into "multiqueue interrupt and queue assignment". > > No need to blow it up into three slots. Agreed; I made the adjustments. James