Re: [Xen-devel] [PATCH v3 ]libxl: allow to set more than 31 vcpus

[Dario Faggioli <raistlin@xxxxxxxx>]

On Fri, 2012-06-01 at 07:18 +0000, Zhang, Yang Z wrote: 
> > > diff -r 3b0eed731020 tools/libxl/xl_cmdimpl.c
> > > --- a/tools/libxl/xl_cmdimpl.c  Fri Jun 01 09:27:17 2012 +0800
> > > +++ b/tools/libxl/xl_cmdimpl.c  Fri Jun 01 10:34:13 2012 +0800
> > > @@ -650,7 +650,14 @@ static void parse_config_data(const char
> > >
> > >      if (!xlu_cfg_get_long (config, "vcpus", &l, 0)) {
> > >          b_info->max_vcpus = l;
> > > -        b_info->cur_vcpus = (1 << l) - 1;
> > > +
> > > +        if (libxl_cpumap_alloc(ctx, &b_info->avail_vcpus, l)) {
> > > +            fprintf(stderr, "Unable to allocate cpumap\n");
> > > +            exit(1);
> > > +        }
> > >
> > ... Do you mind explaining me what would have happened here without your
> > previous patch, i.e., by just using the existing libxl_cpumap_alloc ?
> >
> > I might be wrong, but I was wondering whether it is worth changing the
> > interface like that for just this single case which saves, what, 1 to 3
> > bytes per domain?
> > 
> 
> It's ok to use existing libxl_cpumap_alloc(). But in my case, there is no 
> need to use the existing interface.
>
Ok.

> And, in future, there are some cases may not need to allocate max size cpumap 
> too
> So it's better to extend the current interface.
> 
Well, maybe... Who knows what future reserves ?!? :-D

Anyway, although I see your point, I really really dislike the new
parameter in libxl_cpumap_alloc(), but of course it is not something up
to me to decide, neither it is something I'd loose some sleep for. :-P

Thanks and Regards,
Dario

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

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