linux-kernel - Re: [PATCH -next] RISCV: Add some depends for NUMA

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Date:   Fri, 5 Feb 2021 15:53:21 +0800
From:   Kefeng Wang <wangkefeng.wang@...wei.com>
To:     Palmer Dabbelt <palmer@...belt.com>
CC:     Atish Patra <Atish.Patra@....com>,
        <linux-riscv@...ts.infradead.org>,
        "Paul Walmsley" <paul.walmsley@...ive.com>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -next] RISCV: Add some depends for NUMA


On 2021/2/5 14:58, Palmer Dabbelt wrote:
> On Wed, 03 Feb 2021 06:23:43 PST (-0800), wangkefeng.wang@...wei.com 
> wrote:
>> The numa feature is useless for riscv32 platform(MAXPHYSMEM_1GB if 
>> 32bit),
>
> I'm not convinced of that.  There's no reason NUMA shouldn't work on 
> 32-bit, it
> doesn't depend on having a large amount of memory just having non-uniform
> memory.  I could buy the argument that build a 32-bit NUMA system 
> would be
> wacky, but IIUC it works now and I don't see any reason to throw that 
> away.

I think the RV32 won't benefit from NUMA, there's no too much memory 
support on RV32,

and it may increase the Image size,  so I decided to drop support for RV32.

>
>> and it should depends on SMP feature, this also fix the build error,
>
> I can buy that CONFIG_NUMA doesn't really make sense without 
> CONFIG_SMP, as
> there's not a whole lot to do, but I also don't see any reason from 
> disallowing
> users from picking it.  arm64 allows !SMP && NUMA, and I don't see any 
> reason
> it wouldn't work just as well for us.

ARM64 won' support !SMP after following patch, and for most 
architecture,  the NUMA feature

depends or select SMP feature.


commit 4b3dc9679cf779339d9049800803dfc3c83433d1
Author: Will Deacon <will@...nel.org>
Date:   Fri May 29 18:28:44 2015 +0100

     arm64: force CONFIG_SMP=y and remove redundant #ifdefs



>
>>   riscv64-buildroot-linux-gnu-ld: mm/page_alloc.o: in function `.L0 ':
>>   page_alloc.c:(.text+0x4808): undefined reference to 
>> `node_reclaim_distance'
>
> The only instance of node_reclaim_distance I see in mm/page_alloc.c is 
> already
> guarded with CONFIG_NUMA, but the definition of node_reclaim_distance 
> isn't.
> I'll send out some patches to add the guard which might make sorting 
> this out
> earlier, but I don't see it fixing any failures.
>
>
>