Did AIX actually _allocate_ and map the pages you requested, or merely _reserve_ them by bumping a counter? Solaris at least historically did the latter. The

Did AIX actually _allocate_ and map the pages you requested, or merely _reserve_ them by bumping a counter? Solaris at least historically did the latter. The heavy lifting of determining which physical page you would get, and actually mapping it, was generally still deferred until a fault required it. While paging out to rotational media is a tremendous latency issue, paging out to an NVMe SSD or something like Optane doesn't seem like it is nearly as bad. One could imagine a tiered system of paging also: first by compressing into another RAM location, but then evicting the tail of that compressed page set to SSD as required to make more room in RAM.