usb with fast interrupts

[John-Mark Gurney]

Scott Long wrote this message on Mon, Nov 15, 2004 at 01:05 -0700:
> John-Mark Gurney wrote:
> >Scott Long wrote this message on Fri, Nov 12, 2004 at 14:48 -0700:
> >
> >>M. Warner Losh wrote:
> >>
> >>>Our usb system supports soft interrupts, but we currently don't make
> >>>productive use of them.  The following makes interrupts fast
> >>>interrupts and uses taskqueues to queue data to a SWI.
> >>>
> >>>Lemme know if it works for you.
> >>
> >>Taskqueues aren't good for timing-sensitive operations.  Even though USB
> >>may not be terribly sensitive, I bet you'll actually see performance
> >>drops with things like umass with this.  Could you instead just put the
> >>real handler into a kthread and wake it up, or use a swi?
> >
> >
> >If you need low latency, I made taskqueue's easier to create:
> >TASKQUEUE_DEFINE_THREAD(kqueue);
> >
> >and then use:
> >                taskqueue_enqueue(taskqueue_kqueue, &kq->kq_task);
> >
> >of course replace kqueue w/ your own string...  Check the taskqueue(9)
> >man page for more details.
> >
> 
> So the only problem with TASKQUEUE_DEFINE_THREAD() is that it appears
> impossible at the moment to clean up the thread that this creates when
> the driver wants to unload.

That shouldn't be too hard to fix. :)

-- 
  John-Mark Gurney				Voice: +1 415 225 5579

     "All that I will do, has been done, All that I have, has not."