For every open browser tab and every active user, Jenkins GUI requests updates of the Build Queue and Executor Status (/ajaxBuildQueue and /ajaxExecutors). In our setup, 80 concurrent users require 10 server side cores to just serve these two URLs.

This refresh interval is hardcoded to 5000 ms in hudson-behavior.js in multiple places. It would be nice to somehow consolidate these values and be able to configure them, maybe something along the lines of System property hudson.Functions.autoRefreshSeconds