[$] Managing multiple sources of page-hotness data

Knowing how frequently accessed a page of memory is (its "hotness") is akey input to many memory-management heuristics. Jonathan Cameron, in amemory-management track at the 2025 Linux Storage, Filesystem,Memory-Management, and BPF Summit, pointed out that the number of sourcesof that kind of data is growing over time. He wanted to explore thequestions of what commonality exists between data from those sources, andwhether it makes sense to aggregate them all somehow.