Date: Mon, 15 Nov 2004 00:01:55 -0800 From: John-Mark Gurney <gurney_j@resnet.uoregon.edu> To: Scott Long <scottl@freebsd.org> Cc: "M. Warner Losh" <imp@bsdimp.com> Subject: Re: usb with fast interrupts Message-ID: <20041115080155.GH57546@funkthat.com> In-Reply-To: <41952FBD.40602@freebsd.org> References: <20041112.143439.33211003.imp@bsdimp.com> <41952FBD.40602@freebsd.org>
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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.
--
John-Mark Gurney Voice: +1 415 225 5579
"All that I will do, has been done, All that I have, has not."
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