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Subject: Re: [PATCH] a local-timer-free version of RCU
From: Peter Zijlstra <peterz@infradead.org>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>, Joe Korty <joe.korty@ccur.com>,
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Date: Wed, 10 Nov 2010 18:31:11 +0100
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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();
}