I wasn't aware that this function exists, but then again it is possibly that this function is disabled by a web hoster. Further, you might run into additional timeouts from the web server that you cannot influence from PHP. They might only be triggered if no output is produced for a certain time, but then again it is not practical to produce output while the tag plugin collects matching pages. What you could try is creating a file
inc/preload.php with the content
If you only get blank pages afterwards, just delete the file again, then probably your web hoster doesn't allow changing the time limit.