LRU LinkedHashMap that limits size based on available memory

Question

I want to create a LinkedHashMap which will limit its size based on available memory (ie. when freeMemory + (maxMemory - allocatedMemory) gets below a certain threshold). This will be used as a form of cache, probably using "least recently used" as a caching strategy.

My concern though is that allocatedMemory also includes (I assume) un-garbage collected data, and thus will over-estimate the amount of used memory. I'm concerned about the unintended consequences this might have.

For example, the LinkedHashMap may keep deleting items because it thinks there isn't enough free memory, but the free memory doesn't increase because these deleted items aren't being garbage collected immediately.

Does anyone have any experience with this type of thing? Is my concern warranted? If so, can anyone suggest a good approach?

I should add that I also want to be able to "lock" the cache, basically saying "ok, from now on don't delete anything because of memory usage issues".

Answer 1

I know I'm biased, but I really have to strongly recommend our MapMaker for this. Use the softKeys() or softValues() feature, depending on whether it's GC collection of the key or of the value that more aptly describes when an entry can be cleaned up.