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Date: Sun, 10 Jun 2012 10:54:56 -0700
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
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Subject: Re: [PATCH 0/2] rcu: Extended quiescent state for adaptive nohz
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On Sun, Jun 10, 2012 at 12:58:56AM +0200, Frederic Weisbecker wrote:
> On Thu, Jun 07, 2012 at 03:45:08PM -0700, Paul E. McKenney wrote:
> > > I can see you've implemented a version for TinyRCU. Nohz cpusets only work on
> > > SMP right now because there must be at least one CPU running with the tick
> > > to maintain the timekeeping. I'm pretty confident that one day we'll remove
> > > the jiffies and we'll be able to do the whole timekeeping by using the TSC
> > > or so. There is quite a way before we reach that though.
> > 
> > In the meantime, would it make sense to slow the tick rate by a factor
> > of 10 or so on that one CPU when nothing else is going on?  Or does
> > timekeeping absolutely require running the tick at full speed?
> 
> I'm not sure of the possible consequences of that.

OK, so I will remove the TINY_RCU patches for the moment.  If reducing
tick speed on the sole remaining idle CPU ever becomes feasible and
useful, they are easy to add back in.

							Thanx, Paul