In the Administration Portal, it is possible to set a threshold for cluster level monitoring as a percentage or an absolute value, for example, 95% or 2048 MB. When usage exceeds 95% or free memory falls below 2048 MB, a "high memory usage" or "low memory available" event is logged. This reduces log clutter for clusters with large (1.5 TB) amounts of memory.
This bug has not been marked as blocker for oVirt 4.3.0.
Since we are releasing it tomorrow, January 29th, this bug has been re-targeted to 4.3.1.