3% throughput regression in KV pillowfight on 6.5.0-1818

The regression reproduces on both weekly and daily env. As well as across all pillowfight tests.

2 nodes, 20/80 R/W, 512B  test:

6.5.0-1817:  1.97-1.99M ops/sec 
6.5.0-1818:  1.93-1.96M ops/sec

Changes in 1818:

kv_engine changed from a05e60640a5f613cc08337167e8d655bcf0018f5 to master
[+] b68b803 StoredValue: compare deletionSource in operator==
[+] 56d7227 MB-31978: Use StreamContainer in DcpProducer
[+] 7e76d45 MB-32108: HashTable: introduce Committed & Pending perspectives
[+] aa8e6b0 MB-26907: Enable expiry output integration on DCP consumer
[+] a20202e MB-32001: Update privilege checks for durability dcp messages

Test runs and logs:

6.5.0-1817: http://perf.jenkins.couchbase.com/job/ares/9065/console

6.5.0-1818: http://perf.jenkins.couchbase.com/job/ares/9064/console

cpu profiles attached