Re: [patch] Real-Time Preemption, -RT-2.6.9-mm1-V0.4

[Ingo Molnar]

* Rui Nuno Capela <rncbc@xxxxxxxxx> wrote:

> The following table compares the state between my RT-U3 and RT-V0.4.3
> configurations, regarding only the mentioned options:
> 
>   option                       RT-U3.0    RT-V0.4.3
>   ---------------------------- ---------- ---------
>   CONFIG_DEBUG_SLAB              n          n
>   CONFIG_DEBUG_PREEMPT           y          y
>   CONFIG_DEBUG_SPINLOCK_SLEEP    n          -
>   CONFIG_PREEMPT_TIMING          n          n
>   CONFIG_RWSEM_DEADLOCK_DETECT   -          y
>   CONFIG_FRAME_POINTER           y          y
>   CONFIG_DEBUG_STACKOVERFLOW     y          y
>   CONFIG_DEBUG_STACK_USAGE       n          n
>   CONFIG_DEBUG_PAGEALLOC         n          n
> 
> (dash "-" means that the option is not available in the config).
> 
> As you can see, it can only be CONFIG_RWSEM_DEADLOCK_DETECT, being new
> in RT-V0.4.3, that is probably affecting on RT-V0.4.3. I'll try to
> rebuild and test all over without it, and see if it gets any better.

note that DEBUG_PREEMPT got more expensive in the -V kernels. I'd
suggest to disable all the 'y' ones in both the -U and -V kernel and
compare them then.

but especially the userspace overhead seems to be significantly higher
in the -V kernel so i'm not quite sure it can all be attributed to
debugging overhead. We'll see.

also, how does the context-switching rate compare between the two tests? 
This test is pretty steady when it's running, so the context-switch
rates can be directly compared, correct?

	Ingo
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