Re: [PATCH] arm64: defconfig: enable CONFIG_SCHED_CLUSTER

[Christoph Lameter (Ampere)]

On Wed, 13 Aug 2025, Christoph Lameter (Ampere) wrote:

> 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?

Sorry no that is not correct. The cluster information is correctly read
from the ACPI tables and the cluster ids are avaialble in

	/sys/devices/system/cpu/cpuXX/topology/cluster_id

if CONFIG_SCHED_CLUSTER is enabled.

If there is an issue then it is a problem with the vendor firmware
providing cluster id configurations via ACPI that cause regressions.

We could add a blacklist for those platforms to avoid regressions but we
should not allow that to hinder us to enable full support for clustering
on ARM64.