Messages in this thread | | | Date | Tue, 5 Jun 2012 14:29:47 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH 0/6] x86/cpu hotplug: Wake up offline CPU via mwait or nmi |
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On Tue, Jun 05, 2012 at 09:49:16PM +0200, Peter Zijlstra wrote: > On Tue, 2012-06-05 at 21:43 +0200, Thomas Gleixner wrote: > > Vs. the interrupt/timer/other crap madness: > > > > - We really don't want to have an interrupt balancer in the kernel > > again, but we need a mechanism to prevent the user space balancer > > trainwreck from ruining the power saving party. > > What's wrong with having an interrupt balancer tied to the scheduler > which optimistically tries to avoid interrupting nohz/isolated/idle > cpus?
Such an interrupt balancer would be a good thing, but I don't believe that it will be sufficient.
> > - The timer issue is mostly solved by the existing nohz stuff > > (plus/minus the few bugs in there). > > Its not.. if you create an isolated domain there's no way to expel > existing timers from there.
OK, I'll bite... Why not just use CPU hotplug to expel the timers?
(Sorry, but you just can't expect me to pass that one up!)
> > - The other details (silly IPIs) and cross CPU timer arming) are way > > easier to solve by a proper prohibitive state than by chasing that > > nonsense all over the tree forever. > > But we need to solve all that without a prohibitibe state anyway for the > isolation stuff to be useful.
I bet that we will end up having to do both.
Thanx, Paul
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