Re: [Xenomai-core] [rfc] unit testing context switches.

[Jan Kiszka <jan.kiszka@domain.hid>]

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Gilles Chanteperdrix wrote:
> Now that the big context switches bugs have been solved, here is a patch
> that adds a unit test for context switches and FPU switches
> with various type of threads (kernel, user, user in secondary mode,
> not using FPU, using FPU, etc...).

Very good idea! Maybe it's a start to create more of such useful tests.

> As is the case of the latency test
> there is a small RTDM driver in kernel-space, put in the benchmark
> class, even though this test is for unit testing, not for benchmarking.

"Benchmark" is likely not the right term for such devices anymore. I
guess no one will miss rtbenchmark.h, so what about this:

rttesting.h:
RTDM_CLASS_TESTING
 |
 +-- RTDM_SUBCLASS_TIMER
 |
 +-- RTDM_SUBCLASS_SWITCH

In fact, you may even consider to add some performance tests to your
driver one day. I would find it very interesting to have some numbers on
average domain migration delays or on those various other switching
variants - both from user and kernel contexts. This could then serve
users to decide how to design critical parts of their system (and us to
look for performance regressions).

> 
> The FPU switches need a small piece of code architecture dependent,
> put in <asm/xenomai/fptest.h>, currently only implemented for x86.
> 
> The kernel-space driver is called xeno_switchtest.ko, the user-space
> testing tool is called switchtest, because there is already a context
> switch benchmarking tool called "switch".
> 

By combining both feature sets, the need for different names would
disappear. :)

Jan


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