A shared cache memory system, comprising: a means for associating each cache subdivision of a plurality of cache subdivisions (200 - 200) of the shared cache memory system with a Quality of Service, QoS, class of a plurality of QoS classes; a means for receiving a memory access request comprising a QoS identifier, QoSID; a means for accessing a cache subdivision corresponding to the memory access request among the plurality of cache subdivisions; a means for determining whether the QoSID of the memory access request corresponds to the QoS class of the plurality of QoS classes associated with the cache subdivision; a means for updating a QoSID tracking tag of a plurality of QoSID tracking tags associated with the cache subdivision corresponding to the memory access request based on the means for determining; and a means for generating an approximate usage measurement for the QoS class of the plurality of QoS classes based on the plurality of QoSID tracking tags, characterized in that said means for generating the approximate usage measurement for the QoS class of the plurality of QoS classes, based on the plurality of QoSID tracking tags, comprises: a means for determining a fraction of the plurality of cache subdivisions associated with the QoS class; a means for determining a count of the plurality of cache subdivisions associated with the QoS class for which the associated QoSID tracking tag is set; and a means for dividing the count of the plurality of cache subdivisions by the fraction to generate the approximate usage measurement. a means for associating each cache subdivision of a plurality of cache subdivisions (200 - 200) of the shared cache memory system with a Quality of Service, QoS, class of a plurality of QoS classes; a means for receiving a memory access request comprising a QoS identifier, QoSID; a means for accessing a cache subdivision corresponding to the memory access request among the plurality of cache subdivisions; a means for determining whether the QoSID of the memory access request corresponds to the QoS class of the plurality of QoS classes associated with the cache subdivision; a means for updating a QoSID tracking tag of a plurality of QoSID tracking tags associated with the cache subdivision corresponding to the memory access request based on the means for determining; and a means for generating an approximate usage measurement for the QoS class of the plurality of QoS classes based on the plurality of QoSID tracking tags, characterized in that said means for generating the approximate usage measurement for the QoS class of the plurality of QoS classes, based on the plurality of QoSID tracking tags, comprises: a means for determining a fraction of the plurality of cache subdivisions associated with the QoS class; a means for determining a count of the plurality of cache subdivisions associated with the QoS class for which the associated QoSID tracking tag is set; and a means for dividing the count of the plurality of cache subdivisions by the fraction to generate the approximate usage measurement. a means for determining a fraction of the plurality of cache subdivisions associated with the QoS class; a means for determining a count of the plurality of cache subdivisions associated with the QoS class for which the associated QoSID tracking tag is set; and a means for dividing the count of the plurality of cache subdivisions by the fraction to generate the approximate usage measurement.