This is useful for numa systems (e.g. to track how much time you spend on each numa socket), note that the memcg controller already has numa support. For exampl

This is useful for numa systems (e.g. to track how much time you spend on each numa socket), note that the memcg controller already has numa support. For example, depending on what mempolicy you have configured you may want to know how much memory is allocated on each numa node and also where the processes are mostly running, because remote numa memory accesses are more expensive. This is also generally useful if you're using cpusets (even if you're not on a numa system) because you may have them configured in a way where some CPUs belong to multiple cpusets. You can already get per-cpu CPU usage information, but this could help you figure out why a particular CPU has more usage than another.