Subject: Re: [PATCH v3 0/5] mm: Enable CONFIG_NODES_SPAN_OTHER_NODES by default for NUMA

From: Baoquan He <[email-masked]>
Date: Sun, 29 Mar 2020 08:19:24 +0800

On 03/28/20 at 11:31am, Hoan Tran wrote:
> In NUMA layout which nodes have memory ranges that span across other nodes,
> the mm driver can detect the memory node id incorrectly.
> 
> For example, with layout below
> Node 0 address: 0000 xxxx 0000 xxxx
> Node 1 address: xxxx 1111 xxxx 1111

Sorry, I read this example several times, but still don't get what it
means. Can it be given with real hex number address as an exmaple? I
mean just using the memory layout you have seen from some systems. The
change looks interesting though.

> 
> Note:
>  - Memory from low to high
>  - 0/1: Node id
>  - x: Invalid memory of a node
> 
> When mm probes the memory map, without CONFIG_NODES_SPAN_OTHER_NODES
> config, mm only checks the memory validity but not the node id.
> Because of that, Node 1 also detects the memory from node 0 as below
> when it scans from the start address to the end address of node 1.
> 
> Node 0 address: 0000 xxxx xxxx xxxx
> Node 1 address: xxxx 1111 1111 1111
> 
> This layout could occur on any architecture. Most of them enables
> this config by default with CONFIG_NUMA. This patch, by default, enables
> CONFIG_NODES_SPAN_OTHER_NODES or uses early_pfn_in_nid() for NUMA.
> 
> v3:
>  * Revise the patch description
> 
> V2:
>  * Revise the patch description
> 
> Hoan Tran (5):
>   mm: Enable CONFIG_NODES_SPAN_OTHER_NODES by default for NUMA
>   powerpc: Kconfig: Remove CONFIG_NODES_SPAN_OTHER_NODES
>   x86: Kconfig: Remove CONFIG_NODES_SPAN_OTHER_NODES
>   sparc: Kconfig: Remove CONFIG_NODES_SPAN_OTHER_NODES
>   s390: Kconfig: Remove CONFIG_NODES_SPAN_OTHER_NODES
> 
>  arch/powerpc/Kconfig | 9 ---------
>  arch/s390/Kconfig    | 8 --------
>  arch/sparc/Kconfig   | 9 ---------
>  arch/x86/Kconfig     | 9 ---------
>  mm/page_alloc.c      | 2 +-
>  5 files changed, 1 insertion(+), 36 deletions(-)
> 
> -- 
> 1.8.3.1
> 
> 

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