private boolean scanInProgress() {
    return currentScan != null && !currentScan.isDone();
  }
Determine who/when should invoke scan. Maybe when 10% of the RegionEntries have been dirtied by
{@link RegionEntry#setRecentlyUsed(RegionEntryContext)}.

Determine when to stop scanning.
geode-core/src/main/java/org/apache/geode/internal/cache/eviction/LRUListWithAsyncSorting.java