ContentSummaryComputationContext::nodeIncluded() is being used to keep track of all INodes visited during the current content summary calculation. This can be all of the INodes in the filesystem, making for a VERY large hash table. This simply won't work on large filesystems.
We noticed this after upgrading a namenode with ~100Million filesystem objects was spending significantly more time in GC. Fortunately this system had some memory breathing room, other clusters we have will not run with this additional demand on memory.
This was added as part of
HDFS-10797 as a way of keeping track of INodes that have already been accounted for - to avoid double counting.