linux-kernel - Re: [PATCH] MIPS: Loongson: Use CONFIG_NR_CPUS_DEFAULT

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Date:   Tue, 31 Mar 2020 15:21:00 +0800
From:   Tiezhu Yang <yangtiezhu@...ngson.cn>
To:     Jiaxun Yang <jiaxun.yang@...goat.com>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Huacai Chen <chenhc@...ote.com>
Cc:     linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org,
        Xuefeng Li <lixuefeng@...ngson.cn>
Subject: Re: [PATCH] MIPS: Loongson: Use CONFIG_NR_CPUS_DEFAULT_64 to support
 more CPUs

On 03/31/2020 03:05 PM, Jiaxun Yang wrote:

>
> 于 2020年3月31日 GMT+08:00 下午3:00:06, Tiezhu Yang <yangtiezhu@...ngson.cn> 写到:
>> When I update the mainline kernel on the Loongson 2-way platform which
>> has 8 CPUs, it only shows 4 CPUs due to NR_CPUS is 4, this is obviously
>> wrong.
>>
>> In order to support more CPUs on the Loongson platform, it is better
>> to use CONFIG_NR_CPUS_DEFAULT_64 instead of CONFIG_NR_CPUS_DEFAULT_4
>> to specify the maximum number of CPUs which the kernel will support.
>>
>> Signed-off-by: Tiezhu Yang <yangtiezhu@...ngson.cn>
> Would 16 be a better option?
> We have only 4 way platform.

There maybe have more than 4 cores per CPU or more than 4 ways
in the future, so I think 64 is better, otherwise we need to
modify this configuration once more.

>
>> ---
>> arch/mips/Kconfig | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
>> index a1f973c..a0b11f5 100644
>> --- a/arch/mips/Kconfig
>> +++ b/arch/mips/Kconfig
>> @@ -475,7 +475,7 @@ config MACH_LOONGSON64
>> 	select ISA
>> 	select I8259
>> 	select IRQ_MIPS_CPU
>> -	select NR_CPUS_DEFAULT_4
>> +	select NR_CPUS_DEFAULT_64
>> 	select USE_GENERIC_EARLY_PRINTK_8250
>> 	select SYS_HAS_CPU_LOONGSON64
>> 	select SYS_HAS_EARLY_PRINTK