You might be missing indexes for the reader table, which could cause your
issues.
You'll find information about XWiki  Feed Plugin indexes here:
  I had the same issue (very slow activity stream), and
last week-end it
 suddenly became horribly slow (few minutes for the home page).
 I added missing index, checked it was ok (request indicated from 2s to 0s),
 increased the document store cache to 2000, but it's still horribly slow.
 There are about 10000 rows in table activitystream_events
 (activitystream_events_params is empty), including 4500 just for the Reader
 application ! (with 3 rss feeds registered, each of them having the same
 count of rows wich seems a bit strange).
 What is strange about it is that for home page for example, the page takes
 minutes to show up, and the activity stream displayed at the end is almost
 empty : only new items are shown, as if it had "forgotten" all the past
 history, though activitystream table is far from empty... I really think
 something went bad about the activity streams ...
 Also, individual requests to activitystream_events table seem to be quite
 fast, but requests occur maybe only one per second, making the whole thing
 very slow.
 --
 View this message in context:
 
http://xwiki.475771.n2.nabble.com/Activity-performance-is-slow-tp6961805p69…
 Sent from the XWiki- Users mailing list archive at 
Nabble.com.
 _______________________________________________
 users mailing list
 users(a)xwiki.org
 
http://lists.xwiki.org/mailman/listinfo/users