One embodiment of the present invention provides a system that efficiently marks cache lines in a multi-processor computer system. The system starts by receiving a load request for a cache line from a requesting thread. Upon receiving the load request, the system loads a copy of the cache line into a local cache for the requesting thread. The system then load-marks the copy of the cache line in the local cache by incrementing a reader count value contained in metadata for the copy of the cache line, regardless of the cache coherency protocol status of the copy of the cache line, whereby the system updates the metadata in the local copy of the cache line without obtaining exclusive access to the cache line.