Re: New NUMA scheduler and hotplug CPU

[Andrew Theurer <habanero@us.ibm.com>]

On Monday 26 January 2004 18:07, Nick Piggin wrote:
> >>Well OK, this would require a per architecture function to handle
> >>CPU hotplug. It could possibly just default to arch_init_sched_domains,
> >>and just completely reinitialise everything which would be the simplest.
> >
> >Call me crazy, but why not let the topology be determined via userspace at
> > a more appropriate time?  When you hotplug, you tell it where in the
> > scheduler to plug it.  Have structures in the scheduler which represent
> > the nodes-runqueues-cpus topology (in the past I tried a node/rq/cpu
> > structs with simple pointers), but let the topology be built based on
> > user's desires thru hotplug.
>
> Well isn't userspace's idea of topology just what the kernel tells it?
> I'm not sure what it would buy you... but I guess it wouldn't be too
> much harder than doing it in kernel, just a matter of making the userspace
> API.

Sort of, the cpus to node is pretty much what the kernel says it is, but the 
cpu to runqueue mapping IMO is not a clear cut thing.