Re: [Xen-devel] [PATCH v6 3/7] x86: initialize per socket cpu map

["Xu, Dongxiao" <dongxiao.xu@xxxxxxxxx>]

> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: Monday, January 20, 2014 9:27 PM
> To: Xu, Dongxiao
> Cc: andrew.cooper3@xxxxxxxxxx; dario.faggioli@xxxxxxxxxx;
> Ian.Campbell@xxxxxxxxxx; Ian.Jackson@xxxxxxxxxxxxx;
> stefano.stabellini@xxxxxxxxxxxxx; xen-devel@xxxxxxxxxxxxx;
> konrad.wilk@xxxxxxxxxx; dgdegra@xxxxxxxxxxxxx; keir@xxxxxxx
> Subject: Re: [PATCH v6 3/7] x86: initialize per socket cpu map
> 
> >>> On 05.12.13 at 10:38, Dongxiao Xu <dongxiao.xu@xxxxxxxxx> wrote:
> > For each socket in the system, we create a separate bitmap to tag its
> > related CPUs. This per socket bitmap will be initialized on system
> > start up, and adjusted when CPU is dynamically online/offline.
> 
> There's no reasoning here at all why cpu_sibling_mask and
> cpu_core_mask aren't sufficient.

The new mask is to mark socket CPUs, and they may be different with 
cpu_sibling_mask and cpu_core_mask...

> 
> > --- a/xen/arch/x86/smpboot.c
> > +++ b/xen/arch/x86/smpboot.c
> > @@ -59,6 +59,9 @@ DEFINE_PER_CPU_READ_MOSTLY(cpumask_var_t,
> cpu_core_mask);
> >  cpumask_t cpu_online_map __read_mostly;
> >  EXPORT_SYMBOL(cpu_online_map);
> >
> > +cpumask_t socket_cpu_map[MAX_NUM_SOCKETS] __read_mostly;
> > +EXPORT_SYMBOL(socket_cpu_map);
> 
> And _if_ we really need it, then it should be done in a better way
> than via a statically sized array, the size of which can't even be
> overridden on the build and/or hypervisor command line.

I saw current Xen code uses a lot of such static macros, e.g., NR_CPUS.
This reminds me one thing, can we define the MAX_NUM_SOCKETS as NR_CPUS? Since 
the socket number could not exceeds the CPU number.

> 
> And there shouldn't be EXPORT_SYMBOL() in new, not directly
> cloned hypervisor code either.

Okay, will remove it in following patch.

Thanks,
Dongxiao

> 
> Jan


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel