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From: Kurijn Buys <Kurijn.Buys@open.ac.uk>
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Date: Wed, 11 Dec 2013 14:23:38 +0000
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Subject: Re: [Xenomai] latency spikes under load
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To: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
Cc: Xenomai@xenomai.org


Op 9-dec.-2013, om 15:27 heeft Gilles Chanteperdrix het volgende geschreven=
:

> On 12/09/2013 04:19 PM, Kurijn Buys wrote:
>> Op 5-dec.-2013, om 11:09 heeft Gilles Chanteperdrix het volgende geschre=
ven:
>>
>>> On 12/05/2013 01:44 AM, Kurijn Buys wrote:
>>>>
>>>> Op 4-dec.-2013, om 17:43 heeft Philippe Gerum het volgende geschreven:
>>>>
>>>>> On 12/04/2013 05:03 PM, Gilles Chanteperdrix wrote:
>>>>>> On 12/04/2013 02:19 PM, Philippe Gerum wrote:
>>>>>>> On 12/04/2013 01:00 PM, Gilles Chanteperdrix wrote:
>>>>>>>> Ok, could you push the branch somewhere so that I can try it?
>>>>>>>>
>>>>>>>
>>>>>>> testing/ipipe-3.8-i915-fix
>>>>>>
>>>>>> I could test it, I no longer get high latencies while moving a large
>>>>>> opengl window. So, it looks good.
>>>>
>>>> I've it running as well (with the priority coupling option disabled th=
is time).
>>>
>>> The options I asked you to change were meant to eliminate any possible
>>> source for high latencies in case of bug. You can return to a normal
>>> configuration now: re-enable SMP or APIC if you prefer to remain in
>>> single processor mode, disable the I-pipe tracer if you want to avoid
>>> the overhead, and re-enable priority coupling if you prefer to use it.
>>
>> Re-enabling SMP is fine, but doesn't necessarily seem to improve the lat=
ency.
>> While I'm still having some small pikes, they keep below 60us, so that i=
s fine to me.
>
> If your processor has hyper-threading, you may have much better results
> indeed in single processor mode, but enabling APIC and IO/APIC to avoid
> the spikes you got when using the legacy PIC.

I enabled APIC, and the latency peaks at 16us only now, and even less with =
load.
This also had an effect on my analogy problem, but not completely... I will=
 start a new thread for that...

Thanks a lot already for resolving this issue!
]{urijn

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