Sending Email Notifications After Commenting on a Page Slow Down Confluence

Steps to Replicate

1. Ensure that Mail Server is configured
2. Create a space and add 2000+ watchers to it
3. Enable page profiling and after that, comment on the homepage of the newly created Space
4. Each com.atlassian.confluence.plugins.confluence-email-resources:notification-templates:Confluence.Templates.Mail.Notifications.commentAdd.soy operation takes more than 1 second repeatedly as many times as the number of page/space watchers. In the profiling logs you will see thousands of these:

   2014-07-22 14:40:34,898 DEBUG [cfreq-2] [atlassian.util.profiling.UtilTimerStack] log [149068ms] - /cf/rest/tinymce/1/content/46106955/comment
   ...
     [0ms] - UserAccessor.isDeactivated()
     [27ms] - PermissionManager.hasPermissionNoExemptions()
       [0ms] - UserAccessor.getGroup()
       [1ms] - UserAccessor.hasMembership()
       [16ms] - DefaultSpacePermissionManager.hasPermission(USECONFLUENCE, firstname.lastname, global)
         [0ms] - UserAccessor.isDeactivated()
         [0ms] - UserAccessor.getGroup()
         [1ms] - UserAccessor.hasMembership()
         [0ms] - UserAccessor.getGroup()
         [0ms] - UserAccessor.hasMembership()
         [0ms] - UserAccessor.getGroup()
         [0ms] - UserAccessor.hasMembership()
         [1ms] - UserAccessor.getGroup()
         [0ms] - UserAccessor.hasMembership()
       [0ms] - UserAccessor.getGroup()
       [1ms] - UserAccessor.hasMembership()
       [8ms] - DefaultSpacePermissionManager.hasPermission(VIEWSPACE, firstname.lastname, TST)
         [0ms] - UserAccessor.getGroup()
         [0ms] - UserAccessor.hasMembership()
     [0ms] - UserAccessor.getConfluenceUserPreferences()
     [0ms] - UserAccessor.exists()
     [0ms] - UserAccessor.getPropertySet()
     [0ms] - UserAccessor.getPropertySet()
     [0ms] - FormatSettingsManager.getDateFormat()
     [0ms] - FormatSettingsManager.getDateTimeFormat()
     [0ms] - FormatSettingsManager.getTimeFormat()
     [0ms] - FormatSettingsManager.getDateFormat()
     [0ms] - FormatSettingsManager.getDateTimeFormat()
     [0ms] - FormatSettingsManager.getEditorBlogPostDate()
     [6ms] - LikeManager.hasLike()
     [32ms] - PermissionManager.hasCreatePermission()
       [0ms] - UserAccessor.getGroup()
       [1ms] - UserAccessor.hasMembership()
       [0ms] - UserAccessor.getGroup()
       [0ms] - UserAccessor.hasMembership()
       [31ms] - DefaultSpacePermissionManager.hasPermission(COMMENT, firstname.lastname, TST)
         [0ms] - UserAccessor.getGroup()
         [1ms] - UserAccessor.hasMembership()
         [0ms] - UserAccessor.getGroup()
         [0ms] - UserAccessor.hasMembership()
     [0ms] - PermissionManager.hasCreatePermission()
     [29ms] - LikeManager.hasLike()
     [0ms] - PermissionManager.hasCreatePermission()
     [27ms] - LikeManager.hasLike()
     [23ms] - Rendering velocity template: /styles/default-inline-css.vm
       [12ms] - Parse: /styles/colors-css.vm
         [9ms] - Parse: /styles/aui-overrides-css.vm
         [1ms] - Parse: /styles/labels-css.vm
         [0ms] - Parse: /styles/diffs-css.vm
     [5082ms] - Rendering soy template: com.atlassian.confluence.plugins.confluence-email-resources:notification-templates:Confluence.Templates.Mail.Notifications.commentAdd.soy
       [0ms] - UserAccessor.getPropertySet()
   ...
   

Suggestion
Process the classes above sometime after the comment has been added as a background process.