The cache implementation in the module urn:org:ten60:netkernel:cache:standard is configured by default to be relatively self tuning. It uses soft references to maximise use of available memory whilst keeping as many items available as possible.

The cache operates by using a soft reference to lower value items making them eligible for garbage collection as heap space becomes limited.

The following parameters are tunable:

• Recompute Period The cache requires periodic housekeeping to prune expired items, move low value items to soft references and collect statistics. This value determines the number of 'cache puts' between recomputations of cache state.
• Soft Threshold The hard-soft threshold value per Megabyte of available (GC Baseline) heap. This value is multiplied by available heap to give the cacheability index above which cache items will be turned into soft references and will then become available for garbage collection. A larger value will increase the cacheable lifetime of resources at the expense of larger memory footprint.
• Hard Limit Only lower this value if you cannot successfully regulate memory usage with softThreshold. The maximum number of items the cache will keep as hard references regardless of perceived memory availability. This value should be used as a safety valve. It ensures that in very dynamic situations the memory usage of the cache cannot grow unbounded but when the valve is opened the cache becomes less efficient.

For additional control over the behaviour of soft references see documentation on SoftRefLRUPolicyMSPerMB when running on Sun JVMs.