Event based scheduling and USB.

[Takanori Watanabe]

In message <4CC732C7.50409 at FreeBSD.org>, Alexander Motin wrote:
>Takanori Watanabe wrote:
>> Is this behavior expected, or something wrong?
>> I noticed one of usb host controller device shares HPET irq.
>> When I implement interrupt filter in uhci driver, the load average
>> goes to 0 as before.
>> 
>> 
>> ====
>> % vmstat -i
>> interrupt                          total       rate
>> irq1: atkbd0                         398          2
>> irq9: acpi0                          408          2
>> irq12: psm0                            3          0
>> irq19: ehci1                          37          0
>> irq20: hpet0 uhci0                 35970        230
>> irq22: ehci0                           2          0
>> irq256: em0                            4          0
>> irq257: ahci0                       1692         10
>> Total                              38514        246
>> ===
>
>I haven't noticed that issue and it is surely not expected for me. I
>will try to reproduce it.
>
>Most likely you should be able to avoid interrupt sharing using some
>additional HPET options, described at hpet(4).

Try to disable using shared IRQ with uhci, the IRQ used by HPET become cpu: 
interrupt and certainly load average goes quite low, 
but never transit to C3 state. Using legacy route, it works quite well.