I mean think of low priority service as services that are not latency sensitive (background jobs).

you want those low priory cgroup to use the extra memory if it’s available (not used by a high priority cgroup)

it a high priority cgroup need the memory it steal it from the low priority cgroup up to the minimum guaranteed to this low priority cgroup.

this low priority cgroup memory contention will turns into IO pressure from page faults. Then IO limit on the low priority cgroup will cap how much IO it can generate by throttling it.

Meanwhile the high priority cgroup use it’s guaranteed cpu, guaranteed IO and guaranteed memory with no hiccup.

to learn more check « fbtax2 memory controller configuration » at https://facebookmicrosites.github.io/cgroup2/docs/memory-con...