Re: [PATCH 0/6] x86/cpu hotplug: Wake up offline CPU via mwait ornmi

[Peter Zijlstra]

On Tue, 2012-06-05 at 15:00 -0700, Paul E. McKenney wrote:
> On Tue, Jun 05, 2012 at 11:37:21PM +0200, Peter Zijlstra wrote:
> > On Tue, 2012-06-05 at 14:29 -0700, Paul E. McKenney wrote:
> > > OK, I'll bite...  Why not just use CPU hotplug to expel the timers?
> > 
> > Currently? Can you say: 'kstopmachine'?
> 
> So if CPU hotplug (or whatever you want to call it) stops using
> kstopmachine, you are OK with it?

It would be much better, still not ideal though.

> > But its also a question of interface and naming. Do you want to have to
> > iterate all cpus in your isolated set, do you want to bring them down
> > far enough to physically unplug. Ideally no to both.
> 
> For many use cases, it is indeed not necessary to get to a point where
> the CPUs could be physically removed from the system.  But CPU-failure
> use cases would need the CPU to be fully deactivated.  And many of the
> hardware guys tell me that the CPU-failure case will be getting more
> common, though I sure hope that they are wrong.

Uhm, yeah, that doesn't sound right.

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