Two separate development efforts improve both Raspberry Pi power management and memory efficiency – one using tools built for massive clusters.
NUMA NUMA makes Raspberry Pi become ZOOMA
A set of kernel patches adds "Suspend to idle" (s2idle) support to the kernel for older Pi models. The second patch, from Igalia, brings NUMA support to the Pi 5, which quite unexpectedly boosts performance. As The Register explained back in 2013, NUMA is a technology more commonly seen in clusters, short for non-uniform memory access.
First the energy management support. Although the Pi series is based on mobile phone technology, they are actually small desktop devices, mainly intended to run off the mains. The new code supports Pis based on the Broadcom BCM2835 SoC. This is the older SoC used in the Raspberry Pi 1, 2 and 3, so at the moment this will not help newer Pi 4 or 5 hardware. Developer Stefan Wahren chose to target the older models first because there is more documentation for them.
S2idle is one of four common types of ACPI sleep states, as explained by the Arch wiki. For reasons that we're sure will make sense to someone somewhere, the levels are known as S0, S1, S3 and S4, and if that doesn't make you wince, you can enjoy knowing that the s2idle support puts the machine in the S0 state, and not S2, because there is no S2 level.
