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To: Alexander Motin <mav@FreeBSD.org>
In-reply-to: Your message of "Tue, 26 Oct 2010 22:57:59 +0300."
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Date: Wed, 27 Oct 2010 16:37:02 +0900
From: Takanori Watanabe <takawata@init-main.com>
Cc: freebsd-acpi@FreeBSD.org
Subject: Re: Event based scheduling and USB.
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In message <4CC732C7.50409@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.