> > My guess is that the overhead you're seeing is entirely from the USB host > > adapter having to wake up and check the transport descriptor lists. This > > will only result in the guest being woken if a device actually responds > > (as mentioned above it should not). > > A quick profile on the host side doesn't show this. Instead, I see a > lot of select() overhead. This actually confirms my hypothesis. After fixing the UHCI bug the guest is completely idle, but the host still needs to wake up at 1ms intervals to do UHCI emulation. I can believe that the most visible part of this is the select() syscall. > Surprising as there are ~10 descriptors being > polled, so ~1200 polls per second. Maybe epoll will help here. I'm not sure where you get 1200 from. select will be called once per host wakeup. i.e. if the USB controller is enabled then 1k times per second due to the frame tick. Are you sure there are actually 10 descriptors being polled? Remember that the nfds argument is the value of the largest fd in the set (+1), not the number of descriptors in the set. Paul -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
