On Mon, 7 Nov 2011, Sarah Sharp wrote: > On Fri, Oct 14, 2011 at 08:33:29AM -0600, Greg KH wrote: > > On Fri, Oct 14, 2011 at 10:05:41AM -0400, Alan Stern wrote: > > > No, a much better approach is to remove all limits on individual > > > transfer sizes and instead have a global limit on the total amount of > > > all usbfs buffers in use at any time. Maybe something like 16 MB; at > > > SuperSpeed, that's about about 30 ms worth of data. > > > > That sounds quite reasonable. > > Alan, won't this global limit on the usbfs URB buffer size effect > userspace drivers that are currently allocating large amounts of > buffers, but still respecting individual buffer limit of 16KB? It seems > like the patch has the potential to break userspace drivers. It might indeed. A further enhancement would replace that 16-MB global constant with a sysfs attribute (a writable module parameter for usbcore). Do you have any better suggestions? > I think that Point Grey's USB 3.0 webcam will be attempting to queue a > series of bulk URBs that will be bigger than your 16MB global limit. For SuperSpeed, 16 MB is rather on the low side. For high speed it amounts to about 1/3-second worth of data, which arguably is also a bit low. Increasing the default is easy enough, but the best choice isn't obvious. Alan Stern -- 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
