Teo Camarasu authored Nov 29, 2023 and Marge Bot committed Jul 04, 2024

We use live words rather than live blocks to determine the size of the
heap for determining memory retention.

Most of the time these two metrics align, but they can come apart in
normal usage when using the nonmoving collector.

The nonmoving collector leads to a lot of partially occupied blocks. So,
using live words is more accurate.

They can also come apart when the heap is suffering from high levels
fragmentation caused by small pinned objects, but in this case, the
block size is the more accurate metric. Since this case is best avoided
anyway. It is ok to accept the trade-off that we might try (and
probably) fail to return more memory in this case.

See also the Note [Statistics for retaining memory]

Resolves #23397