Current situation: Having compression enabled - data size = 5 GB, storage size = 1GB
But when data is loaded to RAM, it consumes 5 GB in RAM.

Proposal:
What if the data /working set/ in RAM would be compressed, same as on disk ? So working set in RAM would be 1 GB and not 5GB

Considering a lot of CPUs, the online decompression overhead would be minor.

This would not be of course suitable for super-fast data, but majority of the apps in my company is midsize,low-speed apps. With memory-compression switch we could avoid many situations when working set is above cache and pages must be exchanged with disk and locking the db