Oh, so what I had assumed was some kind of page table fragmentation was in fact due to the number of postgres clients increasing, meaning that the number of pag

Oh, so what I had assumed was some kind of page table fragmentation was in fact due to the number of postgres clients increasing, meaning that the number of page table entries increased due to duplication between processes? That would make sense, in retrospect: the OOMs almost always occurred at the point of highest client load.