Precisely tracking memory usage in multi-process computing environment

Methods, systems, and apparatus, including computer programs encoded on computer storage media, for tracking memory usage. One of the methods includes implementing an instance of a memory usage tracker (MUT) in each process running in a node of a computer system. The MUT initiates a free process for a memory chunk. A current generation of the memory chunk is determined. The MUT determines whether the mapping element's generation precedes the current generation. If the mapping element's generation is old, the MUT treats the long-living rollover account as the owner of the memory chunk to be freed and if the current generation and the mapping element's generation match, then the MUT considers the owner associated with the mapping element as the owner of the chunk. The MUT then adjusts the balance of the determined memory account and/or sub-account and the balance of the mapping element by the freed memory amount.