Re: [PATCH RESEND 05/12] xen: numa-sched: make space for per-vcpu node-affinity

[Dario Faggioli <dario.faggioli@citrix.com>]

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On mer, 2013-11-06 at 14:47 +0000, George Dunlap wrote:
> On 06/11/13 11:41, Dario Faggioli wrote:
> > There's of course the option of renaming XEN_DOMCTL_setvcpuaffinity to
> > XEN_DOMCTL_setvcpuhardaffinity (and, while there, put some '_' in it!
> > )... But is that really an option? And even if it is an option for the
> > hypervisor, and perhaps, libxc, I'm quite sure it's not for libxl... Am
> > I wrong?
> 
> I think vcpuaffinity is a domctl, which means it's a interface to libxc, 
> and thus malleable.  So I *think* we could actually just add a parameter 
> to vcpuaffinity to say "hard" or "soft".  (Correct me if I'm wrong, Jan.)
> 
Ok, that certainly make it a lot easier than I thought. I'll take it
that this also holds for xc_vcpu_setaffinity(), and will add a flag
there too.

> Where we need to consider backwards compatibility is in the libxl 
> interface. 
>
Sure.

> I'm not sure whether the best thing to do there.  I think we 
> can't break the existing API, so we need to keep 
> libxl_set_vcpuaffinity() available for old callers.  Options include:
> * Just add libxl_set_vcpuaffinity_soft(), and leave the first one as it is
>
All these three looks sensible to me. Personally, I think I'd like this
first one the most. Anyway...

> * Add libxl_set_vcpu_affinity_[something]() which takes a soft/hard 
> flag, and deprecate the existing one
> * Redefine libxl_set_vcpuaffinity() to include a soft/hard flag, bumping 
> the API version and having a work-around for old callers.
> 
> IanJ / IanC, any opinions?
> 
... Sure, let's hear the maintainers! :-)
 
Thanks and Regards,
Dario

-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)


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