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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> 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)?

> +
> +    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()?

> @@ -638,6 +649,8 @@ static int cpu_smpboot_alloc(unsigned int cpu)
>      unsigned int order, memflags = 0;
>      nodeid_t node = cpu_to_node(cpu);
>      struct desc_struct *gdt;
> +    unsigned int socket = cpu_to_socket(cpu);
> +
>  
>      if ( node != NUMA_NO_NODE )

Stray blank line being added.

> @@ -717,6 +734,12 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
>  
>      stack_base[0] = stack_start;
>  
> +    socket_cpumask = xzalloc_array(cpumask_var_t, nr_sockets);
> +    if ( !socket_cpumask )
> +        panic("No memory for socket CPU siblings map");
> +    if ( !zalloc_cpumask_var(socket_cpumask) )
> +        panic("No memory for socket CPU siblings cpumask");

Please combine the two if()s to have just a single panic() invocation.
If either fails, it doesn't really matter which one it was.

> --- a/xen/include/asm-x86/smp.h
> +++ b/xen/include/asm-x86/smp.h
> @@ -58,6 +58,15 @@ int hard_smp_processor_id(void);
>  
>  void __stop_this_cpu(void);
>  
> +/*
> + * The value may be greater than the actual socket number in the system and
> + * is considered not to change from the initial startup.
> + */
> +extern unsigned int nr_sockets;

In the comment, instead of "considered" do you perhaps mean
"expected" or even "required"?

> +/* Representing HT and core siblings in each socket */
> +extern cpumask_var_t *socket_cpumask;

Comment style.

Jan


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