Subject: Re: siop(4) and tagged queuing
To: Matthew Jacob <>
From: Manuel Bouyer <>
List: current-users
Date: 10/23/2000 19:29:49
On Mon, Oct 23, 2000 at 10:16:31AM -0700, Matthew Jacob wrote:
> On Mon, 23 Oct 2000, Manuel Bouyer wrote:
> > On Mon, Oct 23, 2000 at 09:58:39AM -0700, Matthew Jacob wrote:
> > > Almost all of your drives will do this- what you need to do is bump
> > > SDOUTSTANDING up above 100 or so in sd.c.
> > 
> > Well, OK, I'll try this on older drives, with a small cache.
> > BTW, is SDOUTSTANDING really used ? It seems that all drivers doing tagged
> > queueing override this by the number of tags they can do (siop does this) ?
> In sdattach:
>         if (sc_link->openings > SDOUTSTANDING)
>                 sc_link->openings = SDOUTSTANDING;
> which throttles things to SDOUTSTANDING.

Ok. I change openings in the SCBUSACCEL ioctl, which I guess happens before

> Be careful about removing this. OpenBSD did this recently with amusing
> breakage.
> The midlayer needs to be a lot smarter about job scheduling so that it
> respects an HBA's openings limit and also w/o letting one spindle saturate a
> system but also w/o artificially limiting things.

Yes, for sure. BTW, siop currently only allows 15 tags per device.
I'm not sure allowing an arbitrary number of commands to be queued would
be a good idea; it could take several seconds for the queue to drain.

Manuel Bouyer, LIP6, Universite Paris VI.