Re: [PATCH 02/37] xen: introduce a Kconfig option to configure NUMA nodes number

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Thu, 23 Sep 2021, Wei Chen wrote:
> Current NUMA nodes number is a hardcode configuration. This
> configuration is difficult for an administrator to change
> unless changing the code.
> 
> So in this patch, we introduce this new Kconfig option for
> administrators to change NUMA nodes number conveniently.
> Also considering that not all architectures support NUMA,
> this Kconfig option only can be visible on NUMA enabled
> architectures. Non-NUMA supported architectures can still
> use 1 as MAX_NUMNODES.

This is OK but I think you should also mention in the commit message
that you are taking the opportunity to remove NODES_SHIFT because it is
currently unused.

With that:

Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>


> Signed-off-by: Wei Chen <wei.chen@xxxxxxx>
> ---
>  xen/arch/Kconfig           | 11 +++++++++++
>  xen/include/asm-x86/numa.h |  2 --
>  xen/include/xen/numa.h     | 10 +++++-----
>  3 files changed, 16 insertions(+), 7 deletions(-)
> 
> diff --git a/xen/arch/Kconfig b/xen/arch/Kconfig
> index f16eb0df43..8a20da67ed 100644
> --- a/xen/arch/Kconfig
> +++ b/xen/arch/Kconfig
> @@ -17,3 +17,14 @@ config NR_CPUS
>         For CPU cores which support Simultaneous Multi-Threading or similar
>         technologies, this the number of logical threads which Xen will
>         support.
> +
> +config NR_NUMA_NODES
> +     int "Maximum number of NUMA nodes supported"
> +     range 1 4095
> +     default "64"
> +     depends on NUMA
> +     help
> +       Controls the build-time size of various arrays and bitmaps
> +       associated with multiple-nodes management. It is the upper bound of
> +       the number of NUMA nodes the scheduler, memory allocation and other
> +       NUMA-aware components can handle.
> diff --git a/xen/include/asm-x86/numa.h b/xen/include/asm-x86/numa.h
> index bada2c0bb9..3cf26c2def 100644
> --- a/xen/include/asm-x86/numa.h
> +++ b/xen/include/asm-x86/numa.h
> @@ -3,8 +3,6 @@
>  
>  #include <xen/cpumask.h>
>  
> -#define NODES_SHIFT 6
> -
>  typedef u8 nodeid_t;
>  
>  extern int srat_rev;
> diff --git a/xen/include/xen/numa.h b/xen/include/xen/numa.h
> index 7aef1a88dc..52950a3150 100644
> --- a/xen/include/xen/numa.h
> +++ b/xen/include/xen/numa.h
> @@ -3,14 +3,14 @@
>  
>  #include <asm/numa.h>
>  
> -#ifndef NODES_SHIFT
> -#define NODES_SHIFT     0
> -#endif
> -
>  #define NUMA_NO_NODE     0xFF
>  #define NUMA_NO_DISTANCE 0xFF
>  
> -#define MAX_NUMNODES    (1 << NODES_SHIFT)
> +#ifdef CONFIG_NR_NUMA_NODES
> +#define MAX_NUMNODES CONFIG_NR_NUMA_NODES
> +#else
> +#define MAX_NUMNODES    1
> +#endif
>  
>  #define vcpu_to_node(v) (cpu_to_node((v)->processor))
>  
> -- 
> 2.25.1
>