How Intel's Clear Linux Team Cut The Kernel Boot Time From 3 Seconds To 300 ms

Intel engineer Feng Tang spoke at this week's Linux Plumbers Conference in Lisbon, Portugal on how the Clear Linux team managed to boot their kernel faster. They started out with around a three second kernel boot time but cut it down to just 300 ms.

Among the optimizations carried out to really speed-up their boot time were ensuring more asynchronous driver probing, only initializing a small amount of RAM at start and then after booted hot-plug the rest of it in parallel via systemd, optimized root file-system mounting, disabling unnecessary kernel modules, and similar approaches.

Moving forward they are still looking at optimizations for the boot process around in-kernel deferred memory initialization, SMP initialization changes, ACPI tweaking, and user-space/systemd optimizations.

Those wanting to learn more about Intel's art to booting the Linux kernel as fast as possible but not at LPC2019 can see Feng's slide deck (PDF) with an overview of these current and possible future Clear Linux optimizations.