First, record what your current boot looks like:
sudo systemd-analyze critical-chain # Boot Chain Analysis
sudo echo 1 > /proc/sys/kernel/numa_balancing
In /etc/default/grub, enter:
GRUB_CMDLINE_LINUX_DEFAULT="numa=on"
Reboot, then:
sudo systemd-analyze critical-chain # Boot Chain Analysis
It shaved 3 seconds off my boot time to run level 5 (the desktop), and the desktop comes up quicker with less of a dark-screen lag between the console boot logging and the desktop. I'm now down to 19.621 seconds.
This is Non-Uniform Memory Access balancing... moving code to the node where it's got fastest access to a CPU. Each core of my CPU is a node and the memory is a node, it shuffles things about to get the shortest distance between core and code.
grep NUMA=y /boot/config-'uname -r'
The forum auto-formatting messes that up... don't use the single quote ('), use the slanted single quote (`).
CONFIG_NUMA=y
CONFIG_AMD_NUMA=y
CONFIG_X86_64_ACPI_NUMA=y
CONFIG_ACPI_NUMA=y
lscpu | grep -i numa
NUMA node(s): 1
NUMA node0 CPU(s): 0-11
Where this really shines is if you've got several servers (such as IBM 3950s) connected together to act as a single server, or a multi-processor server. But even with a single processor (which can enumerate each core as a NUMA node), it helps.