artnoiDec 20, 2020
The Linux kernel includes multiple options and modules for AMD Zen2 x86 architecture. The vanilla kernel (linux) shipped by Arch does not include such configuration, so to get the most out of Zen2 CPUs on Arch, I will have to custom build my kernel.
linux-znver2The Arch User Repositories include kernel package linux-amd-znver2 which is similar to the versatile vanilla Arch Linux kernel (linux), but with AMD Zen2 optimizations and other AMD-platform options. This is good enough for me, because it includes all the modules (both essential and bloated), thus ensuring that my system will work correctly should it need to load some extra modules.
linux-znver2But because unused modules will be compiled, its presence alone wastes build time. I don’t want to build USB support for my PlayStation2 controller on my AMD laptop. This is when I began to find a way to customing the kernel build option (config) further, and led me to write this article as a note to myself.
Be sure that the module dependencies for those modules in HOOKS section of mkinitcpio.conf are available. The same is true for other -dkms modules.
make options I usedIt’s best to read the kernel README before attempting to build the kernel. The official descriptions make XXconfig lists below can be found on the README file.
make localmodconfig - Will use lsmod (or $LSMOD shell variable to the file containing target machine’s lsmod output) to determine which modules will be built. The result will be a very streamlined kernel.make nconfig - ncurses menu for customizing config (Kconfig). Dubbed new menuconfig. Good for manually removing/adding modules without corrupting the config file.make menuconfig - deprecated, use nconfig instead.make olddefconfig - Uses old config, defaults for new options. This is default for our linux-amd-znver2 package. So, to customize config after using our lsmod as a template, add these lines to prepare() section of PKGBUILD: make localmodconfig make nconfig Optionally, use LSMOD=/path/to/file: make LSMOD=/tmp/lsmod localmodconfig make nconfigThe process is simple, but a bit time consuming. First you need to build a vanilla linux-znver2, and then after verifying that it works with your system, tries to minimize the extra modules and decides which ones should be built in or made as LKM. The main criteria to me when deciding whether to build it into the kernel, or as loadable kernel modules in /usr/lib, is the resulting initramfs size.