A method for performing garbage collection involves obtaining a first reference bitmap including a block address and a set of mark bits, obtaining a first reference, identifying a mark bit of the set of mark bits based on the first reference, comparing an address associated with the mark bit with the first reference to generate a comparison, selecting an existing word from a global bit map based on the block address and the comparison, calculating a new word based on the set of mark bits and the existing word, replacing the existing word in the global bit map with the new word, and reclaiming a block of memory for reuse based on the global bit map after replacing the existing word.