linux-kernel - Re: [PATCH v3 1/4] LoongArch: Move CONFIG_HAVE_SETUP_PER_CPU

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Message-ID: <dcf6e475-8219-6b1e-a99b-2cdf1e86289c@loongson.cn>
Date: Fri, 12 Apr 2024 17:27:31 +0800
From: Tiezhu Yang <yangtiezhu@...ngson.cn>
To: Huacai Chen <chenhuacai@...nel.org>
Cc: Thomas Gleixner <tglx@...utronix.de>, Arnd Bergmann <arnd@...db.de>,
 Marc Zyngier <maz@...nel.org>, loongarch@...ts.linux.dev,
 linux-kernel@...r.kernel.org, loongson-kernel@...ts.loongnix.cn
Subject: Re: [PATCH v3 1/4] LoongArch: Move CONFIG_HAVE_SETUP_PER_CPU_AREA
 related code to smp.c



On 04/12/2024 12:12 PM, Huacai Chen wrote:
> On Thu, Apr 11, 2024 at 9:05 AM Tiezhu Yang <yangtiezhu@...ngson.cn> wrote:
>>
>> Currently, if CONFIG_NUMA is not set but CONFIG_SMP is set, the arch
>> specified setup_per_cpu_areas() in arch/loongarch/kernel/numa.c will
>> not be built and the generic setup_per_cpu_areas() in mm/percpu.c is
>> actually used, this is not reasonable and does not work as intended.
> Why is the generic version not reasonable? We need a custom version
> just because it can put the percpu variable in the best node. If NUMA
> disabled, software can only see one node, how to optimize?

The initial aim is to use the arch specific setup_per_cpu_areas()
in any case under CONFIG_SMP, this patch can be dropped if it is
meaningless for the case of !CONFIG_NUMA and CONFIG_SMP.

Thanks,
Tiezhu