Re: [PATCH] arm64: defconfig: enable CONFIG_SCHED_CLUSTER

[Christoph Lameter (Ampere)]

On Wed, 13 Aug 2025, Sudeep Holla wrote:

> > The problem is that this information is being sourced from the ACPI PPTT.
> > The ACPI specification (AFAIK) doesn't define a cluster, so the linux
> > cluster information is being 'invented' based on however the firmware vendor
> > choose to group CPU nodes in the PPTT. Which means its possible for them to
> > unknowingly create clusters, or also fail to create them when they make
> > sense.
>
> +1, completely agree. As Jeremy mentioned, it is hit or miss and cluster
> is loosely defined and IIRC Huawei pushed this based on their platform at
> the time and it did break some benchmarks on few other platforms. So it
> is not a good idea to make it default config IMO.

Can we figure out which platforms benchmarks were affected and why?

It seems the notion of a "cluster" on ARM64 is derived (I guess a better
word than "invented" hehe)  from sibling information instead of PPTT. But
using that information should work fine right?