An appropriate amount of "query_cache" is believed to improve MySQL performance at the expense of available memory. "Appropriate" will vary widely with usage and "performance" on a live site can be elusive. On Ubuntu, the defaults are modest but "work".
I've been working on the performance of my Drupal site and thought I'd share my results to date in case they might help someone else. My baseline performance using out-of-the-box settings was around 28 requests per second, and the end result is a rate of 68 requests per second.
* TOTAL_HTML - Congratulations, the total number of HTML files on this page (including the main HTML file) is 1 which most browsers can multithread. Minimizing HTTP requests is key for web site optimization.