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Date: Wed, 30 Aug 2006 22:29:31 -0700 (PDT)
From: Luben Tuikov <ltuikov@yahoo.com>
Reply-To: ltuikov@yahoo.com
Subject: Re: [PATCH] aic94xx: Increase can_queue and cmds_per_lun
To: James Bottomley <James.Bottomley@SteelEye.com>
Cc: "Darrick J. Wong" <djwong@us.ibm.com>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       linux-scsi@vger.kernel.org, Alexis Bruemmer <alexisb@us.ibm.com>,
       Mike Anderson <andmike@us.ibm.com>,
       Konrad Rzeszutek <konrad@darnok.org>
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--- James Bottomley <James.Bottomley@SteelEye.com> wrote:
> On Wed, 2006-08-30 at 12:04 -0700, Luben Tuikov wrote:
> > > --- a/drivers/scsi/aic94xx/aic94xx_init.c
> > > +++ b/drivers/scsi/aic94xx/aic94xx_init.c
> > > @@ -71,7 +72,7 @@ static struct scsi_host_template aic94xx
> > >       .change_queue_type      = sas_change_queue_type,
> > >       .bios_param             = sas_bios_param,
> > >       .can_queue              = 1,
> > > -     .cmd_per_lun            = 1,
> > > +     .cmd_per_lun            = 2,
> > 
> > Why 2?  Why not 3?  If you can set this to 3, then why not 4?
> > But if you can set it to 4, why not 5?
> > 
> > This value should also be dynamically set, it should depend on
> > the type of LU and it shouldn't be present in the host template.
> > (But that's an architectural argument which leads nowhere on lsml.)
> 
> actually, cmd_per_lun is pretty much a vestigial variable.  It's used
> for the initial queue depth before the driver decides to turn on TCQ.
> Thus, since the non-tagged depth should always only be 1, the only
> useful value to set it to is 1.

Who cares?