Selecting cache transfer policy for prefetched data based on cache test regions

A method, comprising:

• in response to receiving data that requires eviction of a cache entry at a first cache:
• at a first region of the first cache, applying a first transfer policy to select data that was stored at a first cache entry in response to a prefetch request that has not been a target of a demand request to be transferred to a second cache with a status indicating that the data is to be discarded;
• at a second region of the first cache, applying a second transfer policy to select data that was stored at a second cache entry in response to a prefetch request that has not been a target of a demand request to be transferred to the second cache prior to storing the received data at the second cache entry;
• selecting between the first transfer policy and the second transfer policy based on performance characteristics for the first region and the second region to determine a third transfer policy;
• and
• selectively transferring data at a third region of the first cache to the second cache based on the determined third transfer policy.

A processor, comprising:

• a first cache comprising a first region and a second region;
• a second cache;
• and
• a cache controller configured to:
• at the first region, select a first transfer policy for a first cache entry based on whether data is stored at the first cache entry in response to a prefetch request that has not been a target of a demand request;
• at a second region, select a second transfer policy for cache entries independent of whether data is stored at the cache entries of the second region in response to a prefetch request that has not been a target of a demand request;
• and
• selectively transfer data at the first region and the second region to the second cache in response to receiving data at the first cache that requires eviction of a cache entry from the first cache based on the selected transfer policies at the first region and the second region.