12-15-2019, 12:49 PM
(12-15-2019, 05:35 AM)danielt Wrote: Cutting the boot time requires a seriously nasty trick to prevent the kernel scheduling anything in the slow clocked cores during boot. This can also be picked up without a reinstall but you'll probably have to go grubbing about in the installer etc directory to figure it out (/etc/default/u-boot and /etc/tmpfiles.d/00-enable-big-cores.conf, make sure the kernel is at least 5.4.2-2 from the open build service and ensure you update the bootloader with u-boot-update).
You've actually found a somewhat clever hack that shouldn't horribly break anything in the long run. When you described it as "seriously nasty" I was expecting something much nastier.
For those who don't want to go grubbing around in the installer /etc directory, the hack is to set maxcpus=4 on the kernel command line to stop the kernel from using the big cores before cpufreq is loaded, then write to /sys/devices/system/cpu/cpuX/online later in boot to enable them again once cpufreq has brought them to a sane clockspeed.