I had the latest version of WP Super Cache installed on my WordPress site, and it worked fine.
However, I did not want WP Super Cache to cache pages for known users, so in order to improve performance for pages viewed by these users, I installed WP File Cache... and WP Super Cache stopped working. In other words, I found that it took just as long to view pages if I was not logged in as when I was logged in; previously, the loading of these pages was very fast.
After some investigation, I realised that the problem was that I had some code to flush the output buffers early in order for the user to feel that the site was more responsive, rather than waiting for all the response to be returned before sending the output to the client. It seems that WP Super Cache does not like this.
Is there any way I can achieve the early flushing of output while still having WP Super Cache work? Even if I could have some code which detects whether WP Super Cache was active or not before attempting to flush, that would be great.