Messages in this thread | | | Date | Thu, 9 Apr 2015 15:40:40 -0700 | From | Nishanth Aravamudan <> | Subject | Re: Topology updates and NUMA-level sched domains |
| |
On 08.04.2015 [12:52:12 +0200], Peter Zijlstra wrote: > On Wed, Apr 08, 2015 at 12:32:01PM +0200, Brice Goglin wrote: > > Le 07/04/2015 21:41, Peter Zijlstra a écrit : > > > No, that's very much not the same. Even if it were dealing with hotplug > > > it would still assume the cpu to return to the same node. > > > > > > But mostly people do not even bother to handle hotplug. > > > > > > > You said userspace assumes the cpu<->node relation is a boot-time fixed > > one, and hotplug breaks this. > > I said no such thing. Regular hotplug actually respects that relation.
Wel, sort of. If you *just* hotplug a CPU out, your invariant of what CPUs are currently available on what nodes is no longer held. Similarly if you just add a CPU. And means that you could end up using cpumasks that are incorrect if you don't make them at runtime, it seems?
> > How do you expect userspace to handle hotplug? > > Mostly not. Why would they? CPU hotplug is rare and mostly a case of: > don't do that then. > > Its just that some of the virt wankers are using it for resource > management which is entirely misguided. Then again, most of virt is.
I guess that is a matter of opinion.
-Nish
| |