On Wed, 06 Mar 2024 17:45:04 -0800, Christoph Lameter (Ampere) wrote:

Currently defconfig selects NR_CPUS=256, but some vendors (e.g. Ampere
Computing) are planning to ship systems with 512 CPUs. So that all CPUs on
these systems can be used with defconfig, we'd like to bump NR_CPUS to 512.
Therefore this patch increases the default NR_CPUS from 256 to 512.

As increasing NR_CPUS will increase the size of cpumasks, there's a fear that
this might have a significant impact on stack usage due to code which places
cpumasks on the stack. To mitigate that concern, we can select
CPUMASK_OFFSTACK. As that doesn't seem to be a problem today with
NR_CPUS=256, we only select this when NR_CPUS > 256.

[...]

Applied to arm64 (for-next/misc), thanks!

I dropped the config entry and comment, replaced it with a select as per
Mark's suggestion.

[1/1] ARM64: Dynamically allocate cpumasks and increase supported CPUs to 512
      https://git.kernel.org/arm64/c/0499a78369ad

-- 
Catalin


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