linux-kernel - Re: [ANNOUNCE] 3.8-rc6-nohz4

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Message-ID: <20130207173756.GW2632@linux.vnet.ibm.com>
Date:	Thu, 7 Feb 2013 09:37:56 -0800
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Alessio Igor Bogani <abogani@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Chris Metcalf <cmetcalf@...era.com>,
	Christoph Lameter <cl@...ux.com>,
	Geoff Levand <geoff@...radead.org>,
	Gilad Ben Yossef <gilad@...yossef.com>,
	Hakan Akkan <hakanakkan@...il.com>,
	Li Zhong <zhong@...ux.vnet.ibm.com>,
	Namhyung Kim <namhyung.kim@....com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [ANNOUNCE] 3.8-rc6-nohz4

On Thu, Feb 07, 2013 at 12:06:21PM -0500, Steven Rostedt wrote:
> On Thu, 2013-02-07 at 08:30 -0800, Paul E. McKenney wrote:
> 
> > I suspect that removal of jiffies from the kernel will take a few stages,
> > with RCU being one of the laggards for awhile.  Making RCU's state
> > machine depend wholly on process-based execution will take some care
> > and experimentation, especially for extreme and corner-case workloads.
> > For example, having RCU OOM the system just because a specific CPU was
> > unable to run some RCU kthread for an extended time is something to
> > be avoided.  ;-)
> 
> Tickless doesn't mean no timeouts or periodic timers. I think we will
> always have some sort of dynamic tick when needed. It will just be more
> event driven then something that goes off constantly.

As long as we don't end up replacing a single tick with multiple hrtimers
(or whatever), ending up with more overhead and disruption than we
started with.  ;-)

							Thanx, Paul

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