If you have tuned your key buffer and optimized your query cache and yet still find your site struggling, you can make a handful of smaller changes that will add some more speed.
When reading from tables, MySQL has to open the file that stores the table data. How many files it keeps open at a time is defined by the
table_cache setting, which is set to 64 by default. You can increase this setting if you have more than 64 tables, but be aware that Ubuntu imposes limits on MySQL about how many files it can have open at a time. Going beyond 256 is not recommended unless you have a particularly database-heavy site and know exactly what you are doing.
The other thing you can tweak is the size of the read buffer, which is controlled ...