On Mon, 5 Oct 2015, Paul Jones wrote: > >> Any ideas why the driver is requesting varying block sizes? > > > > The usb-storage driver requests what the block layer tells it to > > request. > I’m running a dd with a block size of 64k, so it seems to be > aggregating 2 requests and then splits them again. More or less. The kernel aggregates requests from dd, and then splits them up based on the max_sector value and other requirements. > Note that both machines in question are not doing anything else. > Both machine have a core i5 4690s (quad core 3.2Ghz) with 16GB of RAM, so I am not sure why there is a 35us delay... That's probably just the time needed by the USB hardware plus the overhead involved in interrupt handling. It's negligible in comparison to the time spent in the actual data transfers, anyway. 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
