1. A method for communicating affinity information in a system that includes a plurality of nodes, comprising: causing each node of the plurality of nodes to maintain a set of affinity information by performing the steps of storing, within the set of affinity information, affinity information relating to the node's own use of each object of a plurality of objects; when the node sends a particular type of message to another node, piggy-backing on the message affinity information relating to the node's use of a particular object; and when the node receives a particular type of message from another node, reading from the message piggy-backed affinity information relating to the other node's use of a particular object, and updating the set of affinity information based on the affinity information that was piggy-backed on the message from the other node.