Re: [Fwd: [RFT] major libata update]

[Jeff Garzik <jeff@garzik.org>]

Linus Torvalds wrote:
> On Wed, 17 May 2006, Jens Axboe wrote:
>> Some devices need serialization between them, and the only way to
>> achieve that currently is by sharing a queue.
> 
> Hmm? No. We share the queue for some things, but the most _common_ example 
> of a device that needs serialization between queues is IDE, and we don't 
> share queues there. We have independent queues, they just end up sharing 
> certain infrastructure (tags and locking).

Strongly agreed.

Note that libata uses independent queues, but serializes access to them. 
  This is the sort of "group of queues" infrastructure I find helpful.


> But they _are_ independent, and you can have different elevators, 
> different merging rules, and even different request functions for the 
> different queues - even if they also have some things they share.

Yep.


> And yes, you can see an ATA host as a host in the SCSI sense, but I wanted 

Actually libata presents one Scsi_Host per SATA port on each controller, 
FWIW :)  So the Scsi_Host notion WRT queues _is_ limiting, which is the 
reason why I refer to "group of queues".

	Jeff