[$] Recent work in memory tiering

Tiered-memory systems are built with multiple types of memory, each ofwhich has different performance characteristics. In addition to the usualDRAM, a tiered system might also provide faster high-bandwidth memory orslower CXL memory. On these systems, the placement of memory allocationshas a significant effect on the performance that a workload will obtain.While work on tiered-memory improvements has been ongoing for years, itfeels like the pace has slowed a bit recently. Even so, there are a fewefforts underway, but they are facing questions about whether the tieringdesign makes sense.