linux-kernel - Re: [PATCH] arm64: Kconfig: Increase NR

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Date:   Mon, 11 Jan 2021 21:20:03 -0800
From:   Vanshidhar Konda <vanshikonda@...amperecomputing.com>
To:     Catalin Marinas <catalin.marinas@....com>
Cc:     Randy Dunlap <rdunlap@...radead.org>,
        Will Deacon <will@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        patches@...erecomputing.com
Subject: Re: [PATCH] arm64: Kconfig: Increase NR_CPUS default to 512

On Mon, Jan 11, 2021 at 06:25:27PM +0000, Catalin Marinas wrote:
>On Mon, Jan 11, 2021 at 10:03:18AM -0800, Randy Dunlap wrote:
>> On 1/11/21 9:57 AM, Vanshidhar Konda wrote:
>> > On Mon, Jan 11, 2021 at 10:56:36AM +0000, Will Deacon wrote:
>> >> On Sat, Jan 09, 2021 at 09:36:15PM -0800, vanshikonda@...amperecomputing.com wrote:
>> >>> From: Vanshidhar Konda <vanshikonda@...amperecomputing.com>
>> >>>
>> >>> Increase the default value of NR_CPUS to 512 from 256. This will
>> >>> enable the defconfig kernel to support platforms that have upto
>> >>> 512 cores.
>> >>
>> >> Do we already support such a platform, and what is it? I'm fine with bumping.
>> >> the number, it's just nice to be able to say specifically _why_ we're dong
>> >> it.
>> >
>> > I'm not aware of any publicly available systems that run into the 256
>> > core limitation. At Ampere we have internal systems that would benefit
>> > from this change as they support more than 256 cores.
>>
>> But what does that have to do with the default value?
>> Do you expect to run defconfig kernels?
>> I don't ever expect that.
>
>We still aim for the arm64 defconfig to run on all supported SoCs, even
>if not optimally. Distros indeed tweak the config to their needs.

Would "all supported SoCs" mean only SoCs that are currently available
publicly? Could we include support for SoCs/systems in development but
to be available publicly in the next few years?

Thanks,
Vanshi

>
>-- 
>Catalin