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Re: [libvirt] [PATCH 3] add parameter flags to D.get_cpu_stats()



On Wed, Apr 18, 2012 at 09:18:45AM -0600, Eric Blake wrote:
> On 04/18/2012 05:14 AM, Hu Tao wrote:
> > ---
> >  examples/get_cpu_stats.ml   |    2 +-
> >  libvirt/libvirt.ml          |    2 +-
> >  libvirt/libvirt.mli         |    2 +-
> >  libvirt/libvirt_c_oneoffs.c |    9 +++++----
> >  4 files changed, 8 insertions(+), 7 deletions(-)
> > 
> > +++ b/libvirt/libvirt_c_oneoffs.c
> > @@ -532,20 +532,21 @@ extern int virDomainGetCPUStats (virDomainPtr domain,
> >  #endif
> >  
> >  CAMLprim value
> > -ocaml_libvirt_domain_get_cpu_stats (value domv, value nr_pcpusv)
> > +ocaml_libvirt_domain_get_cpu_stats (value domv, value nr_pcpusv, value flagsv)
> 
> This adds flags support to the per-cpu half of the libvirt API, but you
> are still missing ocaml bindings for the portion of the libvirt API that
> accesses the domain total stats.  Also, I never understood why the
> caller has to know how many cpus they are passing in advance - shouldn't
> the bindings be smart enough to return an appropriately sized array that
> covers all possible cpus without the caller having to pre-specify that
> sizing?
> 
> For comparison, in the python bindings, we expressed things as:
> 
>     if (!PyArg_ParseTuple(args, (char *)"OOi:virDomainGetCPUStats",
>                           &pyobj_domain, &totalbool, &flags))
> 
> so that a user passes in the domain; a choice of whether they want total
> stats (pass true to get a 1-element array back, corresponding to the C
> code passing start_cpu of -1), or per-cpu stats (pass fals to get an
> n-element array back, with each element mapping to a cpu, and with the
> array sized according to all cpus available); and finally a flags parameter.

It's certainly a unusual, and I agree that we should go with the
model used by the Python bindings.

FWIW it's probably because 'nr_pcpus' happens to be available
conveniently as a value in virt-top at the point when 'get_cpu_stats'
is called.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
libguestfs lets you edit virtual machines.  Supports shell scripting,
bindings from many languages.  http://libguestfs.org


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