Re: [PATCH] sched/rt: don't try to balance rt_runtime when it is futile

From: Paul E. McKenney
Date: Sun May 18 2014 - 11:58:47 EST


On Sun, May 18, 2014 at 10:36:41AM +0200, Mike Galbraith wrote:
> On Sat, 2014-05-17 at 22:20 -0700, Paul E. McKenney wrote:
>
> > If you are saying that turning on nohz_full doesn't help unless you
> > also ensure that there is only one runnable task per CPU, I completely
> > agree. If you are saying something else, you lost me. ;-)
>
> Yup, that's it more or less. It's not only single task loads that could
> benefit from better isolation, but if isolation improving measures are
> tied to nohz_full, other sensitive loads will suffer if they try to use
> isolation improvements.

So you are arguing for a separate Kconfig variable that does the isolation?
So that NO_HZ_FULL selects this new variable, and (for example) RCU
uses this new variable to decide when to pin the grace-period kthreads
onto the housekeeping CPU?

Thanx, Paul

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