[HBASE-6404] Collect p95 stats for get/put/delete/next

Author: gauravm

Summary: Collect p95 stats for get / put / delete / next operations by having a histogram and a percentile metric (with percentile = 0.95) for each operation, respectively. The method of stat collections is similar to D715751.

Test Plan: Unit tests and checked on Titan Shadow.

Reviewers: liyintang, adela, manukranthk

Reviewed By: manukranthk

CC: hbase-eng@

Differential Revision: https://phabricator.fb.com/D779670

Task ID: 1200149

git-svn-id: https://svn.apache.org/repos/asf/hbase/branches/0.89-fb@1480004 13f79535-47bb-0310-9956-ffa450edef68
[HBASE-8484] Adding diagnostic messages when the RegionServer hists an IOException in RegionServerReport

Author: manukranthk

Summary: This diff adds instrumentation in the case when we catch IOException in regionserver report.

Test Plan: Tested on Dev Cluster by killing the master.

Reviewers: aaiyer

Reviewed By: aaiyer

Differential Revision: https://phabricator.fb.com/D797516

git-svn-id: https://svn.apache.org/repos/asf/hbase/branches/0.89-fb@1480005 13f79535-47bb-0310-9956-ffa450edef68
[HBASE-8491] Fixing the TestHeapSizes.

Author: manukranthk

Summary: Accounting for the extra references added. Did an absolute count of non static variables and updated accordingly.

Test Plan: Unit Tests

Reviewers: liyintang

Reviewed By: liyintang

CC: hbase-eng@

Differential Revision: https://phabricator.fb.com/D799334

git-svn-id: https://svn.apache.org/repos/asf/hbase/branches/0.89-fb@1480006 13f79535-47bb-0310-9956-ffa450edef68