Re: [Xen-devel] [PATCH v8 01/13] x86: add socket_cpumask

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 29.05.15 at 04:35, <chao.p.peng@xxxxxxxxxxxxxxx> wrote:
> On Thu, May 28, 2015 at 01:38:05PM +0100, Jan Beulich wrote:
>> >>> On 21.05.15 at 10:41, <chao.p.peng@xxxxxxxxxxxxxxx> wrote:
>> > --- a/xen/arch/x86/mpparse.c
>> > +++ b/xen/arch/x86/mpparse.c
>> > @@ -87,6 +87,18 @@ void __init set_nr_cpu_ids(unsigned int max_cpus)
>> >  #endif
>> >  }
>> >  
>> > +void __init set_nr_sockets(void)
>> > +{
>> > +    unsigned int cpus = bitmap_weight(phys_cpu_present_map.mask,
>> > +                                      boot_cpu_data.x86_max_cores *
>> > +                                      boot_cpu_data.x86_num_siblings);
>> 
>> How did you come to this expression for the bitmap size? I.e.
>> why not simply physids_weight(phys_cpu_present_map)?
> 
> physids_weight(phys_cpu_present_map) gives me cpus for all sockets.
> While here the 'cpus' is actually _cpus_per_socket_. I used the max
> possible cpus indicated in cpuid as the upper bound so bitmap_weight()
> returns the actual available cpus on socket 0.

In which case the variable name is badly chosen, or a respective
comment is missing.

>> > +
>> > +    if ( cpus == 0 )
>> > +        cpus = 1;
>> > +
>> > +    nr_sockets = DIV_ROUND_UP(num_processors + disabled_cpus, cpus);
>> > +}
>> 
>> Is there a reason why this can't just be added to the end of the
>> immediately preceding set_nr_cpu_ids()?
> 
> You mean the declaration or invocation? If the former I have no special
> reason for it (e.g. I can change it).

Neither - I just don't see the need for a new function.

Jan


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