boolean isTunerOn() {
    return this.tunerOn;
  }
Manages tuning of Heap memory using <code>HeapMemoryTuner</code>. Most part of the heap memory is
split between Memstores and BlockCache. This manager helps in tuning sizes of both these
dynamically, as per the R/W load on the servers.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/HeapMemoryManager.java