linux-kernel - Re: Large slowdown with 'x86: Avoid invoking RCU when CPU is idle'

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Date:	Fri, 24 Feb 2012 12:20:44 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	paulmck@...ux.vnet.ibm.com
Cc:	Josh Boyer <jwboyer@...hat.com>, linux-kernel@...r.kernel.org,
	kernel-team@...oraproject.org
Subject: Re: Large slowdown with 'x86: Avoid invoking RCU when CPU is idle'

On Fri, 2012-02-24 at 08:51 -0800, Paul E. McKenney wrote:

> But after looking this over, Steven Rostedt's three-patch set should
> suffice:
> 
> 	https://lkml.org/lkml/2012/2/7/231
> 
> The reason that mine are not needed is that the problematic code is
> called -only- from idle, not from process context, and also that the
> problematic code is tracing.  My patch #45 is required for code that is
> called from both process context and from idle.  My patch #46 is required
> for non-tracing uses of RCU from within the idle loop -- along with TBD
> patches to wrap those uses of RCU in the RCU_NONIDLE() macro.
> 
> So again, in your particular case of x86's power-tracing features,
> Steven Rostedt's three-patch series called out above should be all
> that you need.
> 
> I have CCed Steven in case there is some prerequisite to his patch set.

The above link is the RFC, it probably still suffices, but the patches
that are going into mainline are here:

https://lkml.org/lkml/2012/2/13/530
https://lkml.org/lkml/2012/2/13/525
https://lkml.org/lkml/2012/2/13/524

The above is the order to apply them, (patch 3, 4, and 5) even though
they arrived to LKML out of order.

-- Steve


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