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

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Date:   Mon, 11 Jan 2021 18:25:27 +0000
From:   Catalin Marinas <catalin.marinas@....com>
To:     Randy Dunlap <rdunlap@...radead.org>
Cc:     Vanshidhar Konda <vanshikonda@...amperecomputing.com>,
        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 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.

-- 
Catalin