From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org, mingo@elte.hu,
laijs@cn.fujitsu.com, dipankar@in.ibm.com,
akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de,
rostedt@goodmis.org, Valdis.Kletnieks@vt.edu,
dhowells@redhat.com, eric.dumazet@gmail.com, darren@dvhart.com,
fweisbec@gmail.com, sbw@mit.edu, patches@linaro.org
Subject: Re: [PATCH RFC tip/core/rcu] Add callback-free CPUs
Date: Thu, 6 Sep 2012 13:39:57 -0700 [thread overview]
Message-ID: <20120906203957.GW2448@linux.vnet.ibm.com> (raw)
In-Reply-To: <1346955710.18408.58.camel@twins>
On Thu, Sep 06, 2012 at 08:21:50PM +0200, Peter Zijlstra wrote:
> On Thu, 2012-09-06 at 10:46 -0700, Paul E. McKenney wrote:
> > Getting these
> > CPUs into adaptive-tick mode more quickly reduces OS jitter, which is
> > one big expected benefit of adaptive-tick mode.
>
> I'm not sure I agree with that statement. Its a transition thing and
> therefore statistically irrelevant on the whole -- assuming we
> transition rarely.
>
> And for those who cannot deal with the transition effects, a barrier was
> proposed which would wait until the system hit this state -- although
> the specific implementation of this isn't clear yet afaik.
>
> I very much think we should focus on getting adaptive tick working as
> simple as possible and worry about transition effects later, if at all.
I expect that the RT folks will be interested as well, and they will
likely care about the transition effects because they degrade worst-case
behavior.
Thanx, Paul
prev parent reply other threads:[~2012-09-06 20:49 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-05 21:39 [PATCH RFC tip/core/rcu] Add callback-free CPUs Paul E. McKenney
2012-09-05 21:48 ` Peter Zijlstra
2012-09-05 23:44 ` Paul E. McKenney
2012-09-06 10:13 ` Peter Zijlstra
2012-09-06 16:47 ` Paul E. McKenney
2012-09-06 16:58 ` Peter Zijlstra
2012-09-06 17:46 ` Paul E. McKenney
2012-09-06 18:21 ` Peter Zijlstra
2012-09-06 20:39 ` Paul E. McKenney [this message]
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