Disabling EAS

[diepquynh]

Should EAS (Energy Aware Scheduling) be disabled? EAS is a feature implemented in the core Linux kernel scheduler framework to support energy-aware task placement (e.g when to place tasks on a big or little CPU core to save energy). However, it adds a significant amount of extra latency due to expensive calculation for each task placement decision

Since this board is powered using AC power, my suggestion is to simply disable the feature by simply echoing 0 to /proc/sys/kernel/sched_energy_aware to switch to faster CFS (Completely Fair Scheduler) scheduling path

[Joshua-Riek]

By default, the CPU and GPU scaling governor is ondemand and causes significant performance issues. I have a systemd service that will set both to performance to counter this issue. I don't know much about the kernel, but it makes sense due to the previously mentioned scaling governor issues.

Do you know if this has any meaningful performance impact?

[diepquynh]

Explaining how EAS works in detail is actually really tough as it involves a whole bunch of stuffs related to Linux kernel scheduler, but from my experience working with smartphone kernels with EAS enabled, applying to this case is just simply disable it

[diepquynh]

Setting governor to performance does play a part, as that means the current CPU capacity of all CPU cores are capped to their maximum. But since EAS is enabled, it tries to place as many tasks to the little cluster as possible so sometimes you still see stuttering while doing simple tasks like browsing web

[diepquynh]

Looks like Rockchip have their own performance hack too
https://github.com/orangepi-xunlong/linux-orangepi/blob/orange-pi-5.10-rk3588/kernel/sched/fair.c#L6890

[Joshua-Riek]

Thank you for the explanation I think I understand. I will be happy to look into this a bit more, thanks again for the information and recommendation!

[diepquynh]

rk3588s A55 CPU capacity reference. This figure is scaled with 1024. A76 core is right below a few lines
https://github.com/orangepi-xunlong/linux-orangepi/blob/orange-pi-5.10-rk3588/arch/arm64/boot/dts/rockchip/rk3588s.dtsi#L380