Gilles Chanteperdrix wrote:
> Richard Cochran wrote:
>> On Sun, Apr 24, 2011 at 10:15:00PM +0200, Gilles Chanteperdrix wrote:
>>> some temporary results on the benchmark here:
>>> http://www.xenomai.org/~gch/latency-at91sam9263.png
>>>
>>> The worst case latency seems not to vary much over time, it looks like
>>> it is decreasing a bit, but the differences may well be in the
>>> measurement noise. Unlocked context switch actually improves the latency.
>>>
>>> I will update the png as I get new results.
>> Gilles,
>>
>> That is a very interesting graph. It might be nice to have a
>> "performance benchmarks" page on the wiki, including that figure, plus
>> the description of the test setup. I can contribute IXP and some
>> PowerPC results.
>
> Yes, we should set this up. The xeno-test currently in the head branch
> is made to help doing this.
>
>> Regarding the measured performance, the graphs are shaped like the
>> letter, H (or like a Bactrian camel, with two humps).
>>
>> I appears to me that the peaks of the 2.4.10 lines (red, green) are
>> standing clearly to the left of the 2.5.6 lines (blue, purple), by
>> about 10 microseconds. I would say that 2.4.10 outperforms 2.5.6, on
>> average.
>
> I added the average latencies (except for 2.4.10 with the I-pipe 1.14-04
> patch). The peak corresponds roughly to the average "lat max" column in
> latency results.
>
> Both the I-pipe version and Xenomai version seem to contribute to the
> increased average latency.
>
> The unlocked context switch also improves the worst-case at the expense
> of the average.
>
> But there is hope, 2.6.33-1.18-03 introduces pic muting and re-enables
> irq in the middle of gpio demuxing, which seems to improve the average
> latency.
Hi Richard,
I jumped to conclusions too quickly. I am not sure the results I obtain
really are meaningful. I am probably not doing it enough rigorously.
Regards.
--
Gilles.
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