With Rising Arm Core Counts, Linux 5.1+ ARM64 Images Default To 256 Cores Support

As a change in acknowledging the increasing Arm SoC core counts as more vendors take stabs at higher-end server chips, the default 64-bit Arm (ARM64 / AArch64) kernel image as of Linux 5.1 will default to supporting 256 CPUs compared to the current default limit of 64 CPU cores.

This change is about making the default kernel configuration more relevant to systems with increasing Arm core counts in NR_CPUs is now bumped from 64 to 256. Arm developers made the default NR_CPUS change for the default ARM64 Linux kernel configuration with already there are shipping ARM64 platforms having 256 threads and only more to come.

Of course, the Linux kernel can already support more than that, this is just about the default configuration limit for those doing (or relying upon) "defconfig" builds. The default configuration limit isn't artificially kept high as for each core/thread for the NR_CPUS limit, the kernel image size increases by a few kilobytes.

This change is part of the ARM64 updates for Linux 5.1. This pull also has some RAID6 NEON optimizations and other clean-ups.

But chances are you don't have any 256-thread Arm boxes so of immediate interest to more people will likely be the number of new SoCs and Arm boards/devices supported by Linux 5.1.