Richard Cochran wrote:
> On Mon, Apr 11, 2011 at 11:26:33PM +0200, Gilles Chanteperdrix wrote:
>> Wait a minute. You are comparing results obtained after 2 or 3, or 10
>> minutes of runtime? I am not sure such results are meaningful. I do my
>> benchmarks with the noltp_hell test:
> Of course, the longer the test, the more confidence you have.

Not only that. The aim of the test is to trigger the worst case path. I
suspect you can not trigger it with a 10 minutes tests. As you probably
remember, I was once running Xenomai on IXP465, and the latency with
Xenomai 2.4 and FCSE was around 150us. So, I suspect the test you show
us are not really meaningful. Improving the worst case latency sometimes
results in a higher average latency.

Each release of the I-pipe patch is tested with the boards at my
disposal, and the latency on the oldest board I have, a csb637, has been
the same for a long time. But I can test again a 2.4.10 to confirm this.

In any case, if you want to investigate the difference, the best tool is
the I-pipe tracer. As I said, I am not sure it worked with all versions,
but I can help get it working.

> But, when tracking down kernel freezes and toggling two component
> versions and a half dozen CONFIG options, sometimes you do short tests
> just to "sample" the combination.

Exactly, and IMO, we should not get sidetracked in premature statements
and conclusions about performance of the system when we are tracking a
stability issue. Let us solve the stability issue first, then we will
look into any potential performance issue, and we will do it with a
proper load of the system, and with a four hours test.

What compiler are you using by the way?


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