Re: controlling ACPI IRQ routing

[Lee Howard <faxguy@howardsilvan.com>]

Len Brown wrote:
> On Wednesday 02 January 2008 09:11, Dominique Michel wrote:
>   
>> Le Sat, 29 Dec 2007 10:40:20 -0800,
>> Lee Howard <faxguy@howardsilvan.com> a écrit :
>>
>>
>>     
>>> # cat /proc/interrupts
>>>            CPU0      
>>>   0: 1051464247   IO-APIC-edge      timer
>>>   1:          8   IO-APIC-edge      i8042
>>>   8:          0   IO-APIC-edge      rtc
>>>   9:          0   IO-APIC-fasteoi   acpi
>>>  12:        104   IO-APIC-edge      i8042
>>>  14:    9414304   IO-APIC-edge      ide0
>>>  16: 1051172722   IO-APIC-fasteoi   wct4xxp
>>>  19:          1   IO-APIC-fasteoi   eth1
>>>  21:  158008518   IO-APIC-fasteoi   eth0
>>>  22:    6974044   IO-APIC-fasteoi   libata
>>>  23:    7071112   IO-APIC-fasteoi   libata
>>> NMI:          0
>>> LOC: 1051371544
>>> ERR:          0
>>>
>>>
>>>       
>> Based on that, you may want to use rtirq. It is a boot script (need schedutils
>> as dependency) with associated config scripts. http://alsa.opensrc.org/Rtirq
>>
>> In /etc/conf.d/rtirq, you will find:
>>
>> # IRQ thread service names
>> # (space separated list, from higher to lower priority).
>> RTIRQ_NAME_LIST="rtc snd usb i8042"
>>
>> The most important things is that the devices listed here doesn't have any
>> shared IRQ with some other device and that the rtc remain the first listed
>> device (the one with the higer priority), or the system will hang soon or later.
>>
>> This setup is for audio workstation but is very easy to adapt to any kind of
>> work.
>>
>>     
>
> I've got no experience with the thread priority thing above.
> However, the better way to handle quality of service contention
> is to not do the things you don't care about.
>
> Does the system really need HZ=1000?  you could slow that down to 100,
> or run CONFIG_NO_HZ to reduce it even more...
> Also, on a UP, the LAPIC timer interrupt is redundant --
> you could build your kernel w/o APIC support or boot with nolapic.
>
> This would get rid of the only interrupts which are frequent
> enough to be competing with the device, clock ticks.

If I boot with nolapic then XT-PIC is used, and the wcfxo device ends up 
sharing an IRQ with libata which results in worse performance than with 
it the way that it is.

Thanks,

Lee.
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