linux-kernel - Re: [Ksummit-2013-discuss] [ATTEND] scsi-mq prototype discussion

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Message-ID: <1374270366.2266.70.camel@dabdike>
Date:	Fri, 19 Jul 2013 21:46:06 +0000
From:	James Bottomley <jbottomley@...allels.com>
To:	"Nicholas A. Bellinger" <nab@...ux-iscsi.org>
CC:	Jens Axboe <axboe@...nel.dk>, Mike Christie <michaelc@...wisc.edu>,
	"ksummit-2013-discuss@...ts.linuxfoundation.org" 
	<ksummit-2013-discuss@...ts.linuxfoundation.org>,
	linux-scsi <linux-scsi@...r.kernel.org>,
	James Smart <James.Smart@...lex.Com>,
	LKML <linux-kernel@...r.kernel.org>,
	"scameron@...rdog.cce.hp.com" <scameron@...rdog.cce.hp.com>,
	"kmo@...erainc.com" <kmo@...erainc.com>,
	target-devel <target-devel@...r.kernel.org>,
	Hannes Reinecke <hare@...e.de>, Tejun Heo <tj@...nel.org>,
	Christoph Hellwig <hch@....de>,
	Andrew Vasquez <andrew.vasquez@...gic.com>
Subject: Re: [Ksummit-2013-discuss] [ATTEND] scsi-mq prototype discussion

On Fri, 2013-07-19 at 14:22 -0700, Nicholas A. Bellinger wrote:
> On Wed, 2013-07-17 at 04:52 +0000, James Bottomley wrote:
> > On Tue, 2013-07-16 at 15:15 -0600, Jens Axboe wrote:
> > > On Tue, Jul 16 2013, Nicholas A. Bellinger wrote:
> > > > On Sat, 2013-07-13 at 06:53 +0000, James Bottomley wrote:
> 
> <SNIP>
> 
> > > > > Lets start with discussing this on the list, please, and then see where
> > > > > we go from there ...
> > > > > 
> > > > 
> > > > Yes, the discussion is beginning to make it's way to the list.  I've
> > > > mostly been waiting for blk-mq to get a wider review before taking the
> > > > early scsi-mq prototype driver to a larger public audience.
> > > > 
> > > > Primarily, I'm now reaching out to the people most effected by existing
> > > > scsi_request_fn() based performance limitations.  Most of them have
> > > > abandoned existing scsi_request_fn() based logic in favor of raw block
> > > > make_request() based drivers, and are now estimating the amount of
> > > > effort to move to an scsi-mq based approach.
> > > > 
> > > > Regardless, as the prototype progresses over the next months, having a
> > > > face-to-face discussion with the key parties in the room would be very
> > > > helpful given the large amount of effort involved to actually make this
> > > > type of generational shift in SCSI actually happen.
> > > 
> > > There's a certain amount of overlap with the aio/O_DIRECT work as well.
> > > But if it's not a general session, could always be a BOF or something.
> > > 
> > > I'll second the argument that most technical topics probably DO belong
> > > in a topic related workshop. But that leaves us with basically only
> > > process related topics at KS, I don't think it hurts to have a bit of
> > > tech meat on the bone too. At least I personally miss that part of KS
> > > from years gone by.
> > 
> > Heh well, given that most of the block mq discussions at LSF have been
> > you saying you really should get around to cleaning up and posting the
> > code, you'll understand my wanting to see that happen first ...
> > 
> > I suppose we could try to run a storage workshop within KS, but I think
> > most of the mini summit slots have already gone.
> 
> That would be great, given there is a reasonable level of interest from
> various parities, and the pain threshold for existing scsi small block
> random I/O performance is high..
> 
> When will we know if there is a workshop / mini summit slot available..?
> 
> (CC'ing Mike Christie as well for open-iscsi/scsi-mq bits)
> 
> > There's also plumbers
> > if all slots are gone (I would say that, being biased and on the
> > programme committee) Ric is running the storage and Filesystems MC
> > 
> > http://www.linuxplumbersconf.org/2013/ocw/events/LPC2013/tracks/159
> 
> FYI, I'm not trying to 'sell' scsi-mq to the larger community yet, but
> rather interested in getting the right scsi/block/LLD people in the same
> room at KS for an hour or two to discuss implementation details, given
> the scope of the effort involved.

Well, so that's why I think plumbers might be a better venue: we'll have
more of the actual storage people there.  Usually we get at most 2-3
storage people to KS compared to the 25 or so we usually have at LSF ...
that makes KS not a very good venue for storage centric discussions.

James

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