> indeed, if i set the interrupt threshold control to 1 micro-frame (they > default to 8), i get 10-11 sec dd, say, half as slow.
That seems a good change to make. Particularly for usb mass storage, which for some reason emulates a scsi transaction with three usb transfers and therefore three interrupts per r/w operation (send command, recv/send data, recv status). To get anything like maximum throughput, we'd also have to queue all three transfers at once so that the usb controller could schedule them in adjacent microframes (or maybe even the same one?). Sending them separately amd synchronously from the user-space driver will probably take long enough to miss one or more microframes. ¡Hola! Nemo, should the interrupt threshold be set to 1 microframe (125 μs) to get better latency for all devices? I can't see any good reason for wanting to slow interrupts deliberately.
