From mboxrd@z Thu Jan  1 00:00:00 1970
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Subject: Re: CONFIG_NO_HZ_FULL in x86 (32bit)?
Date: Fri, 11 Oct 2013 14:32:49 +0200
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	Frederic Weisbecker <fweisbec@gmail.com>
To: "Koehrer Mathias (ETAS/ESS2)" <mathias.koehrer@etas.com>
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* Koehrer Mathias (ETAS/ESS2) | 2013-10-11 08:32:50 [+0000]:

>Hi all,
Hi Mathias,

>I found out that with the RT_PREEMPT patch for kernel 3.10 there is the cool feature rcu_nocbs (offload RCU callback processing) available which allows to free cores to run single real time user space applications on it.
>This feature depends on CONFIG_NO_HZ_FULL, however this is not available for x86 (32 bit).
>My question is now: Is there a way to get the rcu_nocbs running together with NO_HZ_FULL on a 32bit x86?

I *think* this is because VIRT_CPU_ACCOUNTING_GEN accounts everything in
nsec instead of jiffies and this could be very expensive on 32bit archs
doing 64bit math.
Frederic, is this everything or is there more to it?

>Thanks for any feedback
>
>Best regards
>
>Mathias

Sebastian