Date: Mon, 15 Nov 2004 01:05:37 -0700 From: Scott Long <scottl@freebsd.org> To: John-Mark Gurney <gurney_j@resnet.uoregon.edu> Cc: "M. Warner Losh" <imp@bsdimp.com> Subject: Re: usb with fast interrupts Message-ID: <41986351.2070806@freebsd.org> In-Reply-To: <20041115080155.GH57546@funkthat.com> References: <20041112.143439.33211003.imp@bsdimp.com> <41952FBD.40602@freebsd.org> <20041115080155.GH57546@funkthat.com>
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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. Scott
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