As discussed in this work, objects typically are small, short-lived and frequently accessed during their short life span. Thus object references exhibit certain characteristic properties that make the object fields referred by them suitable candidates to be cached separately in a cache structure known as an Object-cache. An Object-cache is a cache structure, separately designed for caching only objects. It creates a parallel data access path for objects. The object references are directed through the Object-cache while the other references are directed through a regular data cache.
The performance and energy behavior of the benchmark programs was found to be extremely sensitive to the configuration of the Object-cache, when the optimal configuration was determined on a per-application basis. The relationship between the configuration and performance and energy characteristics of a program (of the entire application) can be explained as follows. A direct mapped Object-cache is more energy efficient per access, consuming only about 30% of the energy of a similar sized four-way set associative cache.
This reduction occurs because a direct mapped cache accesses only one tag and data array per access, while a four-way cache accesses four tag and data arrays per access. A direct mapped cache can also have a shorter access time in part because multiple data arrays need not be multiplexed. While a direct-mapped caches hit rate may be acceptable for many applications, for some applications a direct-mapped cache exhibits a very poor hit rate and hence suffers from poor performance and energy consumption.
