linux-kernel - Re: rcu stalls and soft lockups with recent kernels

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Date:	Fri, 18 Mar 2016 03:28:57 +0100
From:	Mike Galbraith <umgwanakikbuti@...il.com>
To:	Ion Badulescu <ionut@...ula.org>, linux-kernel@...r.kernel.org
Subject: Re: rcu stalls and soft lockups with recent kernels

On Wed, 2016-03-16 at 12:15 -0400, Ion Badulescu wrote:
> Just following up to my own email:
> 
> It turns out that we can eliminate the RCU stalls by changing from 
> CONFIG_RCU_NOCB_CPU_ALL to CONFIG_RCU_NOCB_CPU_NONE. Letting each cpu 
> handle its own RCU callbacks completely fixes the problems for us.
> 
> Now, CONFIG_NO_HZ_FULL and CONFIG_RCU_NOCB_CPU_ALL is the default config 
> for fedora and rhel7. Ho-humm...

All RCU offloaded to CPU0 of a big box seems like a very bad idea.

	-Mike