Re: [PATCH 0/6] Optimize the cpu hotplug locking -v2

[Paul E. McKenney]

On Thu, Oct 10, 2013 at 06:50:46PM +0200, Ingo Molnar wrote:
> 
> * Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> 
> > On Thu, Oct 10, 2013 at 04:57:38PM +0200, Ingo Molnar wrote:
> >
> > > So ... why not make it _really_ cheap, i.e. the read lock costing 
> > > nothing, and tie CPU hotplug to freezing all tasks in the system?
> > 
> > Such that we freeze regular tasks in userspace and kernel tasks in their 
> > special freezer callback so as to guarantee minimal state?
> 
> Yes, absolutely.

That does add quite a bit of latency to the hotplug operations, which
IIRC slows down things like boot, suspend, and resume.

							Thanx, Paul

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