2.1, 2.2, 2.3
For now there is no way to get Used\FreeMemory for region in bytes.
MemoryMetrics.getPagesFillFactor() javadoc says that the method return the percentage of space that is still free and can be filled in.
So, I'd think used memory can be calculated as PhysicalMemoryPages*PageSize*FillFactor.
I've tried to use this, but found weir thing.
PFA a repro.
There is 2 node grid with no persistence configure. Topology is stable.
Cache is populated with unique keys (no updates) and observe allocated data pages metric grows constantly as expected.
But the error look too large, used memory (and FillFactor as well) may 2-10+ time differs.
E.g. allocated pages, fillFactor, usedMem (bytes)
node-0: 13789 0.851563 48096032
node-1: 14447 0.781250 46230400
In next second:
node-0: 13958 0.039063 2233280
node-1: 14624 0.347656 20824576