My current settings:
query_cache_size=20M
query_cache_type=1
query_cache_limit=1M
Most of the queries return the exact same set of results (about 15 rows) and occur every few seconds.
Can anyone tell me how to interpret this graph for cache tuning?
Same result doesn't guarantee that the query will get cached. Example >DATE type query is not at all cache friendly because every query will be different even if the result is the same. Take a look at your queries to determine how to make them cachable.
You should know, that if table gets modification all queries derived from this table are invalidated at once. Your table probably gets modification, so your query cache is invalidated.
