MB-7597: adjust the changes for high CPU usage.

Change-Id: Ib5c55a13ad5c99d6c920c9617f67de1899a5474f
Reviewed-on: http://review.couchbase.org/24565
Tested-by: xiaoqin ma <maxiaoqin2005@gmail.com>
Reviewed-by: Jin Lim <jin@couchbase.com>