linux-kernel - Re: [PATCH v3 0/5] mm: Enable CONFIG_NODES_SPAN_OTHER

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Date:   Sun, 29 Mar 2020 08:19:24 +0800
From:   Baoquan He <bhe@...hat.com>
To:     Hoan Tran <Hoan@...amperecomputing.com>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Oscar Salvador <osalvador@...e.de>,
        Pavel Tatashin <pavel.tatashin@...rosoft.com>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Alexander Duyck <alexander.h.duyck@...ux.intel.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        "David S. Miller" <davem@...emloft.net>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        "open list:MEMORY MANAGEMENT" <linux-mm@...ck.org>,
        linux-arm-kernel@...ts.infradead.org, linux-s390@...r.kernel.org,
        sparclinux@...r.kernel.org, x86@...nel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        lho@...erecomputing.com, mmorana@...erecomputing.com
Subject: Re: [PATCH v3 0/5] mm: Enable CONFIG_NODES_SPAN_OTHER_NODES by
 default for NUMA

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
> 
>