Then the linux code won't work on it, have you tried? I've tried a lot
of different IBM models, they all do service interrupts just fine.
> > > They do have the release interrupt.
> >
> > Which we don't use. To be interesting, you need to speculatively turn on
> > the dma engine for each command you want to start. If you don't do that,
> > then it's faster just to poll for release/no-release at command start
> > time.
>
> That's an annoying thing about ATA TCQ: the command _may_ execute
> immediately, or may be queued (even when queue is empty). At least
> that's how I read the code and specs...
That's correct, you can use the release interrupt to get around that...
> > I don't think the multiple pending _and_ active is that big a deal, and
> > besides _everybody_ uses write back caching on IDE which makes TCQ for
> > writes very uninteresting.
> [...]
> > I have to agree with Eric that the largest win is potentially not
> > getting hit by the rotational latency all the time. I don't think you'll
> > get much extra from actually having more than one active from the dma
> > POV.
>
> Yes and no. I am coming from a driver-complexity perspective:
> single-active is more annoying on the driver side.
>
> In terms of drive performance, multiple active probably doesn't make
> a huge difference. In terms of reduction in host CPU usage, there
> is a performance gain there with multiple active.
It should make a non-neglible difference in smart positioning in the
drive, some things just cannot be done in software for this stuff.
-- Jens Axboe- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/