On Sun, 29 Sep 2013, Markus Rechberger wrote: > to follow up I know why it doesn't happen anymore because customers > are using a kernel module which does optimized transfers and > pre-allocated the URBs and transfer buffer in kernelspace, the > interface just copies the datastream to our actual driver which sits > in userspace. > Goal is to get rid of that kernel module which is working around that > allocation bug. > > Allan, Greg, can we add another IOCTL for telling USBFS to not use SG > transfers (it also allocates 15k buffers and will lead to the same > problem)? > The old behavior was already broke, the SG transfers won't improve the > situation in that case either. Then how will not using SG make the situation any better? You'll just be back with the old, broken behavior. > Those Sheevaplugs have 128mb memory, regular routers and NAS systems > don't necessarily have more either. If you're trying to do big I/O transfers with large buffers in a highly memory constrained system, you're already in trouble. Fiddling around with the kernel won't help. In fact, you might find the best answer is to do lots of small transfers (i.e., 8 KB or even 4 KB). 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
