Re: [Xenomai] latency spikes under load

[Kurijn Buys <Kurijn.Buys@open.ac.uk>]

Op 5-dec.-2013, om 00:44 heeft Kurijn Buys het volgende geschreven:

>
> 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 this time). The latency test results in a worst value of 52us (no idea if this is normal, the lat max globally stays between 10 and 30us), but I have no higher pikes under load in each case...
> The other test I mentioned before still has a few measurements that occur at 10us in stead of 1000us... maybe it's an issue with this test...
>
> I have the same oddity as the other time I installed a 3.8 kernel on Ubuntu 10.04:
> -the /proc/ipipe files don't look how they should I guess. The Linux file is full of lines with "__ipipe_do_IRQ" and near the end a line with "__ipipe_do_critical_sync"...
> -the version file only states "1"
> -the xenomai file mainly has lines with "..." and also this critical sync line near the end.
>
> Also, I tried to enable the ipipe tracer but without the "tracing on boot" option, but I can't get it to work now. When I do "echo < 1 /proc/ipipe/trace/enable" (as root), the flag stays on 0. and the frozen file remains empty.

For some unknown reason, now the tracer works (I didn't even do a reboot en the mean time), and now I have difficulties setting trace/enable to 0.

Another latency test had a pike of 62us (but pikes are very rare now, and not dependent on load anymore), which seems related to the ipipe frozen line:
-56!    44.220  __ipipe_spin_lock_irqsave+0x5 (mask_and_ack_8259A+0x22)

>
>>>
>>>
>>
>> Same here.
>>
>> --
>> Philippe.
>

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