linux-kernel - Re: [PATCH] a local-timer-free version of RCU

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Message-ID: <1289410271.2084.25.camel@laptop>
Date:	Wed, 10 Nov 2010 18:31:11 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Lai Jiangshan <laijs@...fujitsu.com>,
	Joe Korty <joe.korty@...r.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	mathieu.desnoyers@...icios.com, dhowells@...hat.com,
	loic.minier@...aro.org, dhaval.giani@...il.com, tglx@...utronix.de,
	linux-kernel@...r.kernel.org, josh@...htriplett.org,
	houston.jim@...cast.net
Subject: Re: [PATCH] a local-timer-free version of RCU

On Wed, 2010-11-10 at 16:54 +0100, Frederic Weisbecker wrote:
> run the sched tick and if there was nothing to do
> for some time and we are in userspace, deactivate it. 

Not for some time, immediately, have the tick track if it was useful, if
it was not, have it stop itself, like:

tick()
{
 int stop = 1;

 if (nr_running > 1)
  stop = 0;

 if(rcu_needs_cpu())
  stop = 0;

 ...


 if (stop)
  enter_nohz_mode();
}


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