linux-kernel - Re: [PATCH] arm64: Kconfig: Enable NODES_SPAN_OTHER

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Date:   Tue, 25 Jun 2019 11:12:45 +0100
From:   Will Deacon <will@...nel.org>
To:     Hoan Tran OS <hoan@...amperecomputing.com>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Open Source Review <OpenSourceReview@...erecomputing.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] arm64: Kconfig: Enable NODES_SPAN_OTHER_NODES config for
 NUMA

On Mon, Jun 24, 2019 at 02:38:28PM +0000, Hoan Tran OS wrote:
> Some NUMA nodes have memory ranges that span other nodes.
> Even though a pfn is valid and between a node's start and end pfns,
> it may not reside on that node.
> 
> This patch enables NODES_SPAN_OTHER_NODES config for NUMA to support
> this type of NUMA layout.
> 
> Signed-off-by: Hoan Tran <Hoan@...amperecomputing.com>
> ---
>  arch/arm64/Kconfig | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 697ea05..21fc168 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -873,6 +873,13 @@ config NEED_PER_CPU_EMBED_FIRST_CHUNK
>  config HOLES_IN_ZONE
>  	def_bool y
>  
> +# Some NUMA nodes have memory ranges that span other nodes.
> +# Even though a pfn is valid and between a node's start and end pfns,
> +# it may not reside on that node.
> +config NODES_SPAN_OTHER_NODES
> +	def_bool y
> +	depends on ACPI_NUMA

How come this is specific to ACPI?

It would be nice if this was the default, given that only ia64, mips and
sh appear to be the only NUMA-capable architectures which don't have it.
In other words, replace the #ifdef CONFIG_NODES_SPAN_OTHER_NODES in
mm/page_alloc.c with #ifdef CONFIG_NUMA.

Will