Re: [Xen-devel] [PATCH v2 11/16] libxc: get and set soft and hard affinity

[Dario Faggioli <dario.faggioli@xxxxxxxxxx>]

On gio, 2013-11-14 at 14:58 +0000, Ian Jackson wrote:
> Dario Faggioli writes ("[PATCH v2 11/16] libxc: get and set soft and hard 
> affinity"):

> > @@ -206,39 +209,119 @@ int xc_vcpu_setaffinity(xc_interface *xch,
> >          goto out;
> >      }
> >  
> > -    local = xc_hypercall_buffer_alloc(xch, local, cpusize);
> > -    if ( local == NULL )
> > +    cpumap_local = xc_hypercall_buffer_alloc(xch, cpumap_local, cpusize);
> 
> Is xc_hypercall_buffer_free idempotent, and is there a way to init a
> hypercall buffer to an unallocated state ?  If so this function could
> be a lot simpler, and it could in particular more clearly not leak
> anything, by using the "goto out" cleanup style.
> 
When I put this together, I followed suit from similar cases (actually,
this is mostly renaming the function and adding a new parameter). This
to say that I don't think it can be done much differently, but yes, I
will check.

> > +/**
> > + * This functions specify the scheduling affinity for a vcpu. Soft
> > + * affinity is on what pcpus a vcpu prefers to run. Hard affinity is
> > + * on what pcpus a vcpu is allowed to run. When set independently (by
> > + * the respective _soft and _hard calls) the effective affinity is
> > + * also returned. What we call the effective affinity it the intersection
> > + * of soft affinity, hard affinity and the set of the cpus of the cpupool
> > + * the domain belongs to. It's basically what the Xen scheduler will
> > + * actually use. Returning it to the caller allows him to check if that
> > + * matches with, or at least is good enough for, his purposes.
> > + *
> > + * A xc_vcpu_setaffinity() call is provided, mainly for backward
> > + * compatibility reasons, and what it does is setting both hard and
> > + * soft affinity for the vcpu.
> > + *
> > + * @param xch a handle to an open hypervisor interface.
> > + * @param domid the id of the domain to which the vcpu belongs
> > + * @param vcpu the vcpu id wihin the domain
> > + * @param cpumap the (hard, soft, both) new affinity map one wants to set
> > + * @param ecpumap the effective affinity for the vcpu
> 
> Either the doc comment, or the parameter name, should make it clear
> that ecpumap is an out parameter.
> 
Ok, will do.

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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