Slowness when saving page after update the image on the page

Here are the steps to reproduce:

1. Create a page with image and text.
2. Save the page and add 20 followers to watch the page.
3. Add or remove one image showing on the page.
4. Save the page.
5. the doeditpage.action was taking more than 2 seconds to finish the job.

• with single node with no extra permission settings and only one user connected, it took around 2 seconds to save the page. Here is the Access log.
• with a cluster of 2 nodes with no extra permission settings and only one user connected, it took around 5 seconds to save the page. Here is the Access log

When there is not watcher on the page, saving the page took less than 1 seconds.