We recently upgraded from HDP 2.4.2 to HDP 2.5.5 and noticed a significant performance regression. Profiling revealed the change was related to MetricsTableAggregateSourceImpl, which was introduced with HBASE-15518 (Add Per-Table metrics back). Now, that bug was fixed in HBase 1.3/1.4/2.0. Release notes state that HDP 2.5.5 packages HBase 1.1.2 and do not mention HBASE-15518 among fixed issues.
The real cause of the performance regression was increased GC time (from 2% to 18% in one particular environment) and, GC tuning aside, I found HBASE-15742 (Reduce allocation of objects in metrics) to be very much relevant to the observed behavior. It certainly is not part of 2.5.5 (based on the collected profiles) but since release notes are not reliable in that regard I wonder if the fix could possibly been integrated in a later release (2.5.6, 2.6.x)? How can I find out?