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xen-devel
RE: [Xen-devel] [PATCH] xen, tools/python/xen: pincpu support vcpus, add
> > "xm pincpu mydom 1 2,4-6" which would allow VCPU 1 of mydom
> to run on
> > CPUs 2,4 and 5 but no others. -1 would still mean "run anywhere".
> > Having this functionality is really important before we can
> implement
> > any kind of CPU load ballancer.
>
> Interesting idea. I don't see anything in the schedulers
> that would take advantage of that sort of definition. AFAIK,
> exec_domains are never migrated unless told to do so via
> pincpu. Does the new scheduler do this? Or is this more of
> setting up the rules that the load balancer would query to
> find out where it can migrate vcpus?
I see having this as a pre-requisite for any fancy new scheduler (or as
a first step, CPU load ballancer). Without it, I think it'll be
scheduling anarchy :-)
> > Secondly, I think it would be really good if we could have some
> > hierarchy in CPU names. Imagine a 4 socket system with dual
> core hyper
> > threaded CPUs. It would be nice to be able to specify the
> 3rd socket,
> > 1st core, 2nd hyperthread as CPU "2.0.1".
> >
> > Where we're on a system without one of the levels of hierarchy, we
> > just miss it off. E.g. a current SMP Xeon box would be "x.y". This
> > would be much less confusing than the current scalar representation.
>
> I like the idea of being able to specify "where" the vcpu
> runs more explicitly than 'cpu 0', which does not give any
> indication of physical cpu characteristics. We would
> probably need to still provide a simple mapping, but allow
> the pincpu interface to support a more specific target as
> well as the more generic.
>
> 2-way hyperthreaded box:
> CPU SOCKET.CORE.THREAD
> 0 0.0.0
> 1 0.0.1
> 2 1.0.0
> 3 1.0.1
>
> That look sane?
Yep, that's what I'm thinking. I think its probably worth squeezing out
unsused levels of hierarchy, e.g. just having SOCKET.THREAD in the above
example. Keeping it pretty generic makes sense too. E.g. imagine a big
ccNUMA system with a 'node' level above that of the actual CPU socket.
Best,
Ian
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