On Fri, 2009-12-04 at 16:02 -0500, Alan Stern wrote: > On Fri, 4 Dec 2009, Pete Zaitcev wrote: > > > On Fri, 4 Dec 2009 11:59:25 -0800, Greg KH <greg@xxxxxxxxx> wrote: > > > On Fri, Dec 04, 2009 at 12:46:57PM -0700, Pete Zaitcev wrote: > > > > > > A user found that copying to a USB disk crowds out ISO transfers > > > > to audio. How is this even possible? FWIW, "a user" being me. > > > > https://bugzilla.redhat.com/show_bug.cgi?id=517438 > > > > > > > > > Whilst starting a Torrent with Transmission on a VFAT USB hard drive, audio > > > > > (through a USB 5.1 sound card) started skipping like nobody's business. > > > > > > > > > ALSA sound/usb/usbaudio.c:882: cannot submit datapipe for urb 0, error -28: not enough bandwidth > > > > > ALSA sound/usb/usbaudio.c:882: cannot submit datapipe for urb 0, error -28: not enough bandwidth > > I would guess that the problem is the extra computational load caused > by running Torrent. I'd say uber-bogus. There's no computation yet, it's Transmission creating the "how many gigs" files for the torrent. If you ran it on ext4 (as I have the exact same drive setup for a couple of days now), there wouldn't be any traffic to speak of, because ext4 can do sparse reservation for files. dd'ing /dev/null to the USB disk would probably have the same effect. The audio device is a "cheap as chips" Aureon MKII 5.1 sound card, with all 6 channels filled up with audio through PulseAudio. > It could prevent the usbaudio driver from running > in a timely fashion (because of the added interrupt latency), thereby > losing its bandwidth allocation. A usbmon trace would tell whether > this is really what's happening. <snip> > > The whole reason for ISO to exist is to receive the guaranteed bandwidth, > > isn't it (see clause 3.3 of 2.0 spec)? > > > > I understand that until the ISO URB is submitted, there's no way for the > > HCD to know that it should allocate the bandwidth. What is our solution, > > then? Should we create some sort of "channels" that allocate the bandwidth > > (what spec calls "prenegotiated")? > > That is more or less our plan (preallocate periodic bandwidth as soon > as a config or an altsetting is installed). It's going to take a while > to implement, however. /me crosses fingers! -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
