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.
>
> The absolute worst case appears to be about the same, or perhaps
> slightly improved in 2.5.6.
>
> So the differences are not huge, but still I think 2.4.10 is looking
> better.
it is true that 2.4.10 had better average latencies, but the worst case
latencies seem to be improving, and I am afraid this is what we are
aiming at...
--
Gilles.
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