wuauserv High CPU Usage Revisited

Wow, I thought wuauserv was bad a week ago when it ran for almost two hours. Today it ran for over two hours fifteen minutes.

2016-07-16 13:47:25:145  376 c08 AU Launched new AU client for directive 'Download Approval', session id = 0x1
2016-07-16 14:18:00:884  376 c08 AU Successfully wrote event for AU health state:0
2016-07-16 16:03:17:531  376 128c Agent   * Added update {87F7FA52-8F77-4D3B-A873-F651F9DF9946}.100 to search result

Oh, and here's what "high CPU usage" looks like:

I traced it's activity using Process Monitor from sysinternals. It spent a lot of time repeatedly checking some registry keys, such as HKLM\SYSTEM\Setup\SystemSetupInProgress. It also wrote to C:\Windows\SoftwareDistribution\DataStore\DataStore.edb, which is over 1 GB in size, and read OBJECTS.DATA and INDEX.BTR in C:\Windows\System32\wbem\Repository. Googling DataStore.edb led me to C:\Windows\System32\esentutl.exe and it's /d option to defragment. So, I tried

C:\Windows\System32\esentutl.exe /d C:\Windows\SoftwareDistribution\DataStore\DataStore.edb

It did not change the size of the file significantly, but I'll see whether it changes the execution time in the future.