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From: Julian Elischer <julian@ref.tfs.com>
Message-Id: <199505090533.WAA18061@ref.tfs.com>
Subject: Re: Tagged Command queueing...
To: msmith@atrad.adelaide.edu.au (Michael Smith)
Date: Mon, 8 May 1995 22:33:09 -0700 (PDT)
Cc: questions@FreeBSD.org
In-Reply-To: <199505090128.KAA26642@genesis.atrad.adelaide.edu.au> from "Michael Smith" at May 9, 95 10:58:56 am
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> 
> Greetings people!
> 
> First, the obligatory thanks to the FreeBSD team, they do seem to deserve
> it 8)
> 
> I've been following -hackers and -questions for a while now, and the
> subject of SCSI Tagged Command support has come up a number of times,
> in conjunction with (I believe) the adaptec driver.
> 
> I currently run a couple of Ultrastor 34F controllers, which have
> proven extremely reliable and (going by the numbers posted here off and on)
> very quick.  The literature for these controllers indicates that they
> support TCQ, and the disks I'm using support it as well.
The disk driver will queue several commands to the board at once
for each drive. (if the driver tells it it can)
I assume that the board will do TQ if it get's the oportunity..

> 
> The question is; does the FreeBSD driver?  If not, will it at some stage?
> 
> AdvThanksance.
> 
> (Hi julian E! Thanks for the help back when I was getting this thing sorted 8)
you're welcome
> 
> Mike Smith
> Genesis Software
> 
As for teh ultrastore controller,
look for:
        /*
         * fill in the prototype scsi_link.
         */
        uha->sc_link.adapter_unit = unit;
        uha->sc_link.adapter_targ = uha->our_id;
        uha->sc_link.adapter = &uha_switch;
        uha->sc_link.device = &uha_dev;
        uha->sc_link.flags = SDEV_BOUNCE;

and add to it:
	uha->sc_link.opennings = 2;

this will tell teh scsi code it can send upto two commands at
a time to each disk...
try iozone before and after and let me know if it changes?

(I hadn't realised that that driver was single-threading it's commands..)

take a backup first :)    it might confuse the driver/scsi-system 
if they can't handle 2 requests..

(later we can try 3,4,5 :)

julian