linux-kernel - Re: [PATCH tip/core/rcu 07/86] rcu: Force per-rcu

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Message-ID: <20110502102515.GD2297@linux.vnet.ibm.com>
Date:	Mon, 2 May 2011 03:25:15 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Josh Triplett <josh@...htriplett.org>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu, laijs@...fujitsu.com,
	dipankar@...ibm.com, akpm@...ux-foundation.org,
	mathieu.desnoyers@...ymtl.ca, niv@...ibm.com, tglx@...utronix.de,
	peterz@...radead.org, rostedt@...dmis.org, Valdis.Kletnieks@...edu,
	dhowells@...hat.com, eric.dumazet@...il.com, darren@...art.com,
	patches@...aro.org, "Paul E. McKenney" <paul.mckenney@...aro.org>
Subject: Re: [PATCH tip/core/rcu 07/86] rcu: Force per-rcu_node kthreads
 off of the outgoing CPU

On Sun, May 01, 2011 at 08:10:35AM -0700, Josh Triplett wrote:
> On Sun, May 01, 2011 at 06:20:47AM -0700, Paul E. McKenney wrote:
> > From: Paul E. McKenney <paul.mckenney@...aro.org>
> > 
> > The scheduler has had some heartburn in the past when too many real-time
> > kthreads were affinitied to the outgoing CPU.  So, this commit lightens
> > the load by forcing the per-rcu_node and the boost kthreads off of the
> > outgoing CPU.  Note that RCU's per-CPU kthread remains on the outgoing
> > CPU until the bitter end, as it must in order to preserve correctness.
> > 
> > Also avoid disabling hardirqs across calls to set_cpus_allowed_ptr(),
> > given that this function can block.
> 
> This seems like two separate changes in one patch.  The change to
> kernel/rcutree_plugin.h seems entirely separable from the change to
> kernel/rcutree.c here.
> 
> > Signed-off-by: Paul E. McKenney <paul.mckenney@...aro.org>
> > Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> 
> Heh, amusingly this actually seems meaningful, if you intend it as a
> "role" approval.

Yep, that is the intent!  ;-)

							Thanx, Paul
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