Re: PATCH [5/15] qla2xxx: SG tablesize update

[James Bottomley <James.Bottomley@steeleye.com>]

On Sun, 2004-03-14 at 15:36, Jeff Garzik wrote:
> On Sun, Mar 14, 2004 at 09:59:55AM -0500, James Bottomley wrote:
> > The Qla chips are rather weird in that they have a single issue queue
> > (whose size you can vary) but whose entry formats are fixed.  If I
> > remember correctly, an initial command can have 4 SG elements, but a
> > follow on entry can have 7 (not sure of the figures).  But anyway, large
> > SG commands end up having to find multiple entries in this queue (and
> > being a single issue queue for the entire card, it has to be mutexed
> > while you search).  The more resources you need, the more difficult the
> > search and the more contention you generate on the resource mutex.
> 
> The block layer can handle this type of hardware just fine ;-)
> 
> In my SATA hacking I am finding several devices that one must constrain
> based on hardware-global resources, rather than just TCQ (or lack
> thereof).

I'm sorry, I must have missed the multiple queues down to a single HBA
queue API in the block layer, which one is it again?

James