confluence 5.9.1 rebuild Index so slow and high cpu use

confluence 5.9.1 rebuild Index so slow and high cpu use:
The same database content,rebuid Index on confluence 5.8.17 just cost 21min, but in confluence 5.9.1 rebuild need 40hours and too high cpu use
the same at confluence data center 5.9.1 single node

environment
OS: Ubuntu 12.04.4 LTS
DB:Mysql 5.6.25-log MySQL Community Server
java:java version "1.8.0_65"
app:confluence 5.9.1

In my test environment

Confluence Usage
Total Spaces 4579
Site Spaces 263
Personal Spaces 4316
Content (All Versions) 3244179
Content (Current Versions) 1179626
Local Users 47158
Local Groups 8150