Since IBM Connections 5.5, the implementation of the "Link to files" dialogue around files pagination has changed compared to previous release. When you open "Link to files" for linking files into Activities, Wikis, Blogs etc, the dialogue uses several http requests to gather the full list of files to populate the UI selection file picker segment. When the community has several hundred files (eg 800) then 7 extra http requests are sent (1 request per 100 files due to the pagination in the GET request parameter). Each request results in a large amount of data to be received and processed.
In IBM Connections 5.0, pagination has been implemented by displaying page numbers and letting the user click on the specific page to retrieve the list of files. The first page only displayed the first 10 files without impact to rendering performance.