Re: [PATCH tip/core/rcu 31/86] rcu: further lower priority in rcu_yield()

Mike Galbraith
2011-05-02T09:33:16Z

On Mon, 2011-05-02 at 01:11 -0700, Paul E. McKenney wrote:
> On Sun, May 01, 2011 at 07:51:04PM +0200, Mike Galbraith wrote:
> > On Sun, 2011-05-01 at 06:21 -0700, Paul E. McKenney wrote:
> > > From: Paul E. McKenney <paul.mckenney@linaro.org>
> > >
> > > Although rcu_yield() dropped from real-time to normal priority, there
> > > is always the possibility that the competing tasks have been niced.
> > > So nice to 19 in rcu_yield() to help ensure that other tasks have a
> > > better chance of running.
> >
> > But.. that just prolongs the pain of overhead you _have_ to eat, no? In
> > a brief surge, fine, you can spread the cost out.. but how do you know
> > when it's ok to yield?
>
> I modeled this code on the existing code in ksoftirqd. But yes, this is
> a heuristic. I do believe that it is quite robust, but time will tell.

(It probably is fine, but when I see 'yield', alarms and sirens go off)