# Enable RCU priority boosting

## aCOSwt

I just discover with the 3.1.6 kernel new opportunities for tuning the RCU system.

1/ CONFIG_RCU_BOOST_PRIO

 *Quote:*   

> This option specifies the real-time priority to which preempted RCU readers are to be boosted.  If you are working with CPU-bound real-time applications, you should specify a priority higher then the highest-priority CPU-bound application.
> 
> Specify the real-time priority, or take the default if unsure.
> 
> Symbol: RCU_BOOST_PRIO [=1]
> ...

 

Being said that, as part of my /etc/security/limits.conf, I defined a maximum real time priority of 99 for a users group.

Do I understand correctly that, in order for the boost to be efficient in any case, I should :

Set RCU_BOOST_PRIO to 99 AND reduce to 98 the maximum real time priority as defined in my limits.conf ?

2/ RCU_BOOST_DELAY

 *Quote:*   

> This option specifies the time to wait after the beginning of a given grace period before priority-boosting preempted RCU readers blocking that grace period.
> 
> Note that any RCU reader blocking an expedited RCU grace period is boosted immediately.
> 
> Accept the default if unsure.
> ...

 

Is there a simple & userland way to trace the results with different values for this parameter ?

(BTW, I already tried to enable the tracing as provided in kernel but I find the informations I gather more software debugging than tuning oriented)

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## kernelOfTruth

been some time - but:

http://ck-hack.blogspot.co.at/2013/05/bfs-0430-ck1-for-linux-39x.html?showComment=1370195365827#c1514157982143292385

yeah - seems to be totally the case

i'll give these values a try

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