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   systemd.resource-control    ( 5 )

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UNIFIED AND LEGACY CONTROL GROUP HIERARCHIES

The unified control group hierarchy is the new version of kernel control group interface, see Control Groups v2[2]. Depending on the resource type, there are differences in resource control capabilities. Also, because of interface changes, some resource types have separate set of options on the unified hierarchy.

CPU CPUWeight= and StartupCPUWeight= replace CPUShares= and StartupCPUShares=, respectively.

The "cpuacct" controller does not exist separately on the unified hierarchy.

Memory MemoryMax= replaces MemoryLimit=. MemoryLow= and MemoryHigh= are effective only on unified hierarchy.

IO "IO"-prefixed settings are a superset of and replace "BlockIO"-prefixed ones. On unified hierarchy, IO resource control also applies to buffered writes.

To ease the transition, there is best-effort translation between the two versions of settings. For each controller, if any of the settings for the unified hierarchy are present, all settings for the legacy hierarchy are ignored. If the resulting settings are for the other type of hierarchy, the configurations are translated before application.

Legacy control group hierarchy (see Control Groups version 1[3]), also called cgroup-v1, doesn't allow safe delegation of controllers to unprivileged processes. If the system uses the legacy control group hierarchy, resource control is disabled for the systemd user instance, see systemd(1).