A system includes detection of a first allocation of a first memory size in an object store for storage of a first logical page, in response to detection of the first allocation, incrementing a count associated with the first memory size by a first data structure associating a respective count with each of a plurality of memory sizes, detection of a first deallocation of the first logical page, in response to detection of the first deallocation, decrementing a count associated with a second one of the plurality of memory sizes by the first data structure, and determination of a memory usage associated with the object store based on the counts associated with each of the plurality of memory sizes by the first data structure wherein the second one of the plurality of memory sizes is different from the first memory size.