From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kashyap Desai Subject: RE: [PATCH] hpsa: scsi-mq support Date: Mon, 14 Nov 2016 16:35:04 +0530 Message-ID: <6105636cc4a0ef42d47eb426d91634dd@mail.gmail.com> References: <1478879194-32529-1-git-send-email-hare@suse.de> <20161111163532.GA14922@infradead.org> <39d1198d-eb49-71ed-9139-f0efd9eefd0d@suse.com> <20161112173223.GA22158@infradead.org> <20161113115841.GA4818@lst.de> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Return-path: Received: from mail-qk0-f169.google.com ([209.85.220.169]:35668 "EHLO mail-qk0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932970AbcKNLFH (ORCPT ); Mon, 14 Nov 2016 06:05:07 -0500 Received: by mail-qk0-f169.google.com with SMTP id n204so90830254qke.2 for ; Mon, 14 Nov 2016 03:05:07 -0800 (PST) In-Reply-To: <20161113115841.GA4818@lst.de> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Christoph Hellwig , Hannes Reinecke Cc: Christoph Hellwig , Hannes Reinecke , "Martin K. Petersen" , James Bottomley , Don Brace , linux-scsi@vger.kernel.org, Jens Axboe > -----Original Message----- > From: linux-scsi-owner@vger.kernel.org [mailto:linux-scsi- > owner@vger.kernel.org] On Behalf Of Christoph Hellwig > Sent: Sunday, November 13, 2016 5:29 PM > To: Hannes Reinecke > Cc: Christoph Hellwig; Hannes Reinecke; Christoph Hellwig; Martin K. Petersen; > James Bottomley; Don Brace; linux-scsi@vger.kernel.org; Jens Axboe > Subject: Re: [PATCH] hpsa: scsi-mq support > > On Sun, Nov 13, 2016 at 10:44:47AM +0100, Hannes Reinecke wrote: > > One day to mark with bright red in the calendar. > > > > Christoph Hellwig is telling me _NOT_ to use scsi-mq. > > That's not what I'm doing. > > > This patch was done so see what would needed to be done to convert a > > legacy driver. > > As I was under the impression that scsi-mq is the way forward, seeing > > that it should be enabled per default. > > But I must have been mistaken. Apparently. > > What I am doing is to tell you you should not expose multiple queues unless the > hardware actually has multiple submissions queues. The blk-mq and scsi-mq > code works just fine with a single submission queue, and the hpsa driver in > particular works really well with scsi-mq and a single submission queue. E.g. the > RAID HBA on slide 19 of this presentations is an hpsa one: I have similar results for MegaRaid where seen MR driver gives significant improvement for Single Submission Queue and multiple Completion Queue. Having said that scsi-mq is enabled but with single Queue is more than enough to maximize improvement of SCSI-MQ. Major advantage was seen while IO load is cross the boundary of Physical CPU socket. >>From this discussion I understood that - Similar logical changes proposed for megaraid_sas and we are not really going to gain with fake multiple submission exposed to SML. Kashyap > > http://events.linuxfoundation.org/sites/events/files/slides/scsi.pdf > -- > To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of > a message to majordomo@vger.kernel.org More majordomo info at > http://vger.kernel.org/majordomo-info.html