compaction_proactiveness

file: /proc/sys/vm/compaction_proactiveness
variable: vm.compaction_proactiveness

Official reference

This tunable takes a value in the range [0, 100] with a default value of

1. This tunable determines how aggressively compaction is done in the background. Write of a non zero value to this tunable will immediately trigger the proactive compaction. Setting it to 0 disables proactive compaction.

Note that compaction has a non-trivial system-wide impact as pages belonging to different processes are moved around, which could also lead to latency spikes in unsuspecting applications. The kernel employs various heuristics to avoid wasting CPU cycles if it detects that proactive compaction is not being effective.

Setting the value above 80 will, in addition to lowering the acceptable level of fragmentation, make the compaction code more sensitive to increases in fragmentation, i.e. compaction will trigger more often, but reduce fragmentation by a smaller amount. This makes the fragmentation level more stable over time.

Be careful when setting it to extreme values like 100, as that may cause excessive background compaction activity.