StatsDawg

This graph shows information about the query cache. Specifically, it shows how much of the query cache is in use as well as the hit rate. Since the query cache is a coarsely-grained cache, the hit rate may be somewhat low in regular work-loads, however extremely low numbers may indicate that the query cache may not be useful enough to be effective.

Similarly, if you find that the memory usage of the query cache is close to 100%, you may want to consider increasing the query cache as this can indicate that there is not enough space in the cache to store all of the queries that could be cached. Keep in mind, however, that in most configurations, the query cache should not exceed 128MB. You can set the size of the cache by manipulating the query_cache_size varialble.