On Tue, Apr 19, 2011 at 11:32 AM, Cyril Hrubis <[email protected]> wrote:
> Hi!
>> > I don't see any way to find out range from user-space.
>> > Even with CONFIG_SCHED_DEBUG, sched_domain->level isn't exported to /proc.
>> >
>> > I think whole test isn't much useful, as it is very unlikely
>> > you would have all scheduling domains available:
>> > http://lxr.linux.no/#linux+v2.6.38/kernel/sched.c#L6995
>> >
>> > Quoting Peter Zijlstra:
>> > "More like, use sched_debug boot parameter and see your dmesg output.
>> > I've recently merged a patch that makes the whole level thing completely
>> > dynamic, there's no more fixed levels."
>> >
>> > At the moment, I'm out of ideas how to find out acceptable range.
>>
>> Just make the test only run on kernels without that particular
>> functionality. I assume that's possible in some way, or was the author
>> not nice enough to do that (I have to remember that this is Linux and
>> sane versioning with kernel/userland sources, etc aren't commonplace
>> like BSD)?
>
> It's more complicated than that. There are several kernel constants that
> are considered internal, these may be changed by config knobs
> architecture or particular commit. And sometimes there is no way to get
> these from running kernel (as it doesn't make sence to get them until
> you are trying to test that particular part of the kernel works some
> way).
>
> Even more the kernel is every changing codebase, so what was influenced
> by constant may not exist anymore (and the interface for userspace
> don't need to be changed at all) just internal implementation.
>
> And if that's the case. I would rather get rid of test that rely on some
> kernel internals and speculated behaviour, rather than spending eternity
> patching it for each release.
Fair enough. It would be nice if there was some way to expose this
information via debug /proc (or better -- /sys) entries though.
Otherwise doing graybox / whitebox testing of the Linux kernel is
impossible.
Thanks,
-Garrett
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