RE: [Xen-devel] [PATCH 2/3] xend: Add multiple cpumasks support

["Ian Pratt" <m+Ian.Pratt@xxxxxxxxxxxx>]

> > Either Keir's cpu[X] = "Y" approach or my cpu = [ "A","B","C" ]
approach
> > seem workable.
> 
> Your last email seemed to indicate to me that you didn't like using
> quoted values in a list to separate per-vcpu cpumask values.  Maybe I
> was mistaken.

If it's an honest python list I have no problem. Your example appeared
to be some quoting within a string.

> > Keir's approach is rather ill defined if someone tries using both
cpu=
> > and cpu[X]= in the same config file, but I don't see that as a big
> > problem.  Take your pick :-)
> 
> I'm leaning toward the list notation since I already have code that
> parses that properly.

My approach is a list too...

> > BTW: does the right thing happen in the face of vcpu hot plugging?
i.e.
> > if I unplug a vcpu and put it back in do I keep the old mask? If I
add
> > vcpus what mask do they get?
> 
> unplug events only affect a vcpu's status.  The internal struct
> vcpu in the hypervisor is not de-allocated/re-allocated during hotplug
> events.
> 
> We don't currently support a hotadd for vcpus that weren't allocated
at
> domain creation time.  The current method for simulating hot-add would
> be to start a domain with 32 VCPUS and disable all by the number of
> vcpus you currently want.  Ryan Grimm posted a patch back in February
> that had xend do this by adding a new config option, max_vcpus, which
> was used when calling xc_domain_max_vcpus() having the hypervisor
alloc
> that max number of vcpus and then using the vcpus parameter to
determine
> how many to bring online.

I like the idea of having a vcpus_max

> > We should probably add a 'vcpu-pin' variant that enables the mask to
be
> > set for all vcpus. Perhaps '-1' for the vcpu number? Or should we
add
> > 'vcpu-pin-all'?
> 
> vcpu-pin using -1 is probably the quickest, least intrusive method to
> get this behavior.  We could also use a keyword, all for instance:
> 
> xm vcpu-pin vm1 all 0-4,^5

Nice.

> > [secondly, what do you think about implicitly defaulting the mask to
all
> > 1's if the first item in a cpu mask is an exclusion? e.g. ^1]
> 
> That makes sense.  I'll include a patch in the set to add this
behavior.

Thanks,
Ian

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