On Sat, 28 Sep 2013, Markus Rechberger wrote: > > Actually I observed both throughput and cpu utilization can be improved > > with the 4GB of DMA limit on either 32bit arch or 64bit arch, wrt. direct I/O > > over usb mass storage block device. > > > > I didn't look into the sg API in detail yet, but isn't it doing a > copy_to_user still? SG has nothing to do with moving data to or from userspace. The copy_to_user takes place in usbfs, not in the SG code. See copy_urb_data_to_user() in devio.c. 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
