Re: [Xenomai] High latency and smi with intel vendor chip

[Jan Kiszka <jan.kiszka@siemens.com>]

On 2013-06-24 08:40, Jan Kiszka wrote:
> On 2013-06-22 13:57, Franz Engel wrote:
>> Franz Engel wrote:
>>> Jan Kiszkas wrote:
>>>> Franz Engel wrote:
>>>> Hi,
>>>>
>>>> In my dmesg I get the following message:
>>>> dmesg | grep -i xeno
>>>> [    4.478964] I-pipe: head domain Xenomai registered.
>>>> [    4.494089] Xenomai: hal/x86_64 started.
>>>> [    4.505969] Xenomai: scheduling class idle registered.
>>>> [    4.521300] Xenomai: scheduling class rt registered.
>>>> [    4.538525] Xenomai: real-time nucleus v2.6.2.1 (Day At The Beach)
>>> loaded.
>>>> [    4.559065] Xenomai: debug mode enabled.
>>>> [    4.579351] Xenomai: SMI-enabled chipset found
>>>> [    4.592628] Xenomai: SMI workaround failed!
>>>> [    4.605677] Xenomai: starting native API services.
>>>> [    4.619979] Xenomai: starting POSIX services.
>>>> [    4.633088] Xenomai: starting RTDM services.
>>>>
>>>>
>>>> And I have very high latencies. I read that I should try to insert my
>>> the ID of my LCP into the /usr/src/xenomai/ksrc/arch/x86/smi.c file.
>>>
>>> That is no longer true since 2.6.2.1. Xenomai already detects your LPC
>>> (see above), but the BIOS has apparently locked SMI disabling down.
>>>
>>> In this case, you may want to play with smi_mask (see documentation of
>>> "SMI_EN - SMI Control and Enable Register" in the Intel chipset
>>> manuals) to see if disabling of individual SMI features work. If not,
>>> the board is useless for low-latency real-time purposes.
>>
>> I found the documentation for my chipset. But I'm not sure with the
>> interpretation. I think that chapter 13.8.3.11 "SMI_EN-SMI Control and
>> Enable Register"
>> (http://www.intel.com/content/dam/doc/datasheet/io-controller-hub-10-family-
>> datasheet.pdf) is the chapter that descript the options for SMI. But I don't
>> know how to interpret it. It would be very nice if somebody could look into
>> and say me how to understand it and how I can use this information to reduce
>> my latency (if possible).
> 
> Try to clear bits 18, 17, 14, 13, 11, 6 and 3.
> 
> You can also use smictrl [1] for these experiments. Maybe you have to
> add your chipset in this case (it still uses explicit chipset listings,
> need to port Xenomai's logic over), but you won't have to reboot for this.

Just removed this limitation, smictrl now works like Xenomai /wrt
detecting compatible chipsets.

Jan

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