linux-kernel - Re: [PATCH RESEND 0/1] AHCI: Optimize interrupt processing

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Date:	Mon, 29 Jul 2013 12:11:06 -0700
From:	"Nicholas A. Bellinger" <nab@...ux-iscsi.org>
To:	Tejun Heo <tj@...nel.org>
Cc:	Jens Axboe <axboe@...nel.dk>,
	Alexander Gordeev <agordeev@...hat.com>,
	James Bottomley <James.Bottomley@...senPartnership.com>,
	Mike Christie <michaelc@...wisc.edu>,
	linux-kernel@...r.kernel.org, linux-ide@...r.kernel.org,
	Jeff Garzik <jgarzik@...ox.com>,
	linux-scsi <linux-scsi@...r.kernel.org>
Subject: Re: [PATCH RESEND 0/1] AHCI: Optimize interrupt processing

On Mon, 2013-07-29 at 07:50 -0400, Tejun Heo wrote:
> Yo,
> 
> On Fri, Jul 26, 2013 at 05:43:13PM -0700, Nicholas A. Bellinger wrote:
> > Considering there can be more than a single ata_device hanging off each
> > ata_port, the '*sdev = ap->link.device[0].sdev' in __ata_qc_from_tag()
> > is definitely bogus, but I'm not sure how else to correlate
> > blk-mq/scsi-mq per device descriptors to existing code expecting
> > ata_port->qcmd[] descriptors to be shared across multiple devices..
> > 
> > Tejun..?
> 
> I have no idea.  Let's please just do simpler conversion and worry
> about embedding qc's into scsi_cmnds later.  libata isn't a normal
> SCSI driver and has a rather its own thick midlayer doing the
> impedance matching inbetween && I really don't think there is too much
> benefit to be reaped from embedding qc's into scsi_cmnds.
> 

That is essentially the same conclusion that I came to, but wanted to at
least give you a chance to comment here.  ;)

So that said, I'll include a simple conversion for libata into the
scsi-mq WIP branch, and folks who are interested in more detailed
conversions can pursue them as separate items.

--nab 

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