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

[Rui Nuno Capela]

Ingo Molnar wrote:
>
> * Rui Nuno Capela 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?
>

OK. That was it. After switching off CONFIG_RWSEM_DEADLOCK_DETECT on
RT-V0.4.3, I can say that it's now on par to RT-U3.

Later today, I will conduct some extendeded testing, where I'll able to
compare the jackd performance between vanilla, RT-U3 and RT-V0.4.3, on my
UP laptop. All kernel configurations will be stripped off from all the
debug options.

I will take note of xrun rate, jackd scheduling delay histogram, and cpu
usage. Context switch rate will be also acquainted.

Anything else?
-- 
rncbc aka Rui Nuno Capela
rncbc@xxxxxxxxx

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