Re: high load with usb device

["David S. Ahern" <daahern@cisco.com>]

On 09/14/10 10:29, Michael Tokarev wrote:

> For comparison, here's the same strace stats without -usbdevice:
> 
> % time     seconds  usecs/call     calls    errors syscall
> ------ ----------- ----------- --------- --------- ----------------
>  97.70    0.080237          22      3584           select
>   1.09    0.000895           0      6018      3584 read
>   0.33    0.000271           0      9670           clock_gettime
>   0.31    0.000254           0      6086           gettimeofday
>   0.26    0.000210           0      2432           rt_sigaction
>   0.17    0.000137           0      3653           timer_gettime
>   0.15    0.000122           0      2778           timer_settime
>   0.00    0.000000           0         1           ioctl
>   0.00    0.000000           0         1           rt_sigpending
>   0.00    0.000000           0         1         1 rt_sigtimedwait
> ------ ----------- ----------- --------- --------- ----------------
> 100.00    0.082126                 34224      3585 total
> 
> Yes, it is still doing lots of unnecessary stuff, but the load
> is <1%.

Without a USB device attached the controller is turned off. See the call
to qemu_del_timer() in uhci_frame_timer(). As soon as you add the tablet
device the polling starts (see qemu_mod_timer in  uhci_ioport_writew)
and the cpu load starts.

David


> 
> (This is without host_alarm_handler() in qemu_notify_event())
> 
> /mjt
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