Andrea Righi e9ac6105c7 scx_rustland_core: introduce low-power mode ... Introduce a low-power mode to force the scheduler to operate in a very non-work conserving way, causing a significant saving in terms of power consumption, while still providing a good level of responsiveness in the system. This option can be enabled in scx_rustland via the --low_power / -l option. The idea is to not immediately re-kick a CPU when it enters an idle state, but do that only if there are no other tasks running in the system. In this way, latency-critical tasks can be still dispatched immediately on the other active CPUs, while CPU-bound tasks will be forced to spend more time waiting to be scheduled, basically enforcing a special CPU throttling mechanism that affects only the tasks that are not latency critical. The consequence is a reduction in the overall system throughput, but also a significant reduction of power consumption, that can be useful for mobile / battery-powered devices. Test case (using `scx_rustland -l`): - play a video game (Terraria) while recompiling the kernel - measure game performance (fps) and core power consumption (W) - compare the result of normal mode vs low-power mode Result: Game performance | Power consumption | ------------+-----------------+-------------------+ normal mode | 60 fps | 6W | low-power mode | 60 fps | 3W | As we can see from the result the reduction of power consumption is quite significant (50%), while the responsiveness of the game (fps) remains the same, that means battery life can be potentially doubled without significantly affecting system responsiveness. The overall throughput of the system is, of course, affected in a negative way (kernel build is approximately 50% slower during this test), but the goal here is to save power while still maintaining a good level of responsiveness in the system. For this reason the low-power mode should be considered only in emergency conditions, for example when the system is close to completely run out of power or simply to extend the battery life of a mobile device without compromising its responsiveness. Signed-off-by: Andrea Righi <andrea.righi@canonical.com>		2024-05-15 20:32:05 +02:00
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intf.h	scx_rustland_core: use a separate field to store dispatch flags	2024-04-23 16:10:56 +02:00
main.bpf.c	scx_rustland_core: introduce low-power mode	2024-05-15 20:32:05 +02:00