linux-kernel - Re: [PATCH] arch/sh/: fix NUMA build errors

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Date:   Sun, 24 Nov 2019 08:24:58 -0800
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Rich Felker <dalias@...c.org>,
        Linux-sh list <linux-sh@...r.kernel.org>
Subject: Re: [PATCH] arch/sh/: fix NUMA build errors

On 11/19/19 1:12 PM, Randy Dunlap wrote:
> On 11/18/19 11:38 PM, Geert Uytterhoeven wrote:
>> Hi Randy,
>>
>> On Tue, Nov 19, 2019 at 1:55 AM Randy Dunlap <rdunlap@...radead.org> wrote:
>>> From: Randy Dunlap <rdunlap@...radead.org>
>>> Fix SUPERH builds that select SYS_SUPPORTS_NUMA but do not select
>>> SYS_SUPPORTS_SMP and SMP.
>>>
>>> kernel/sched/topology.c is only built for CONFIG_SMP and then the NUMA
>>> code + data inside topology.c is only built when CONFIG_NUMA is
>>> set/enabled, so these arch/sh/ configs need to select SMP and
>>> SYS_SUPPORTS_SMP to build the NUMA support.
>>>
>>> Fixes this build error in 3 different SUPERH configs:
>>>
>>> mm/page_alloc.o: In function `get_page_from_freelist':
>>> page_alloc.c:(.text+0x2ca8): undefined reference to `node_reclaim_distance'
>>>
>>> Signed-off-by: Randy Dunlap <rdunlap@...radead.org>
>>> Reported-by: Geert Uytterhoeven <geert@...ux-m68k.org>
>>> Cc: Yoshinori Sato <ysato@...rs.sourceforge.jp>
>>> Cc: Rich Felker <dalias@...c.org>
>>> Cc: linux-sh@...r.kernel.org
>>> ---
>>> or maybe these should be fixed in the defconfig files?
>>>
>>> or alternatively, does it make any sense to support NUMA without SMP?
>>
>> I think it does.  From arch/sh/mm/Kconfig config NUMA help:
>>
>>         Some SH systems have many various memories scattered around
>>         the address space, each with varying latencies. This enables
>>         support for these blocks by binding them to nodes and allowing
>>         memory policies to be used for prioritizing and controlling
>>         allocation behaviour.
> 
> Yes, I saw that and suspected it also.
> 
> I was (and still am) hoping that a SuperH maintainer comments on
> this and on how they are currently building kernels for these
> failing configs.  Maybe they have some patches that aren't in-tree yet?
> 

Yoshinori-san,
Can you share with us how you build kernels for SUPERH configs that set
CONFIG_NUMA but do not set CONFIG_SMP?  Do you have any patches for this?


> 
>> Probably the NUMA-core is too server/x86-centric, by assuming NUMA is
>> used only on systems with multiple CPUs, each with their own RAM.

Yes, I looked at all of that code for a couple of days and got nowhere
with trying to separate NUMA from SMP.

thanks.
-- 
~Randy