An apparatus comprises processing circuitry for accessing data in a physically-indexed cache. Set indicator recording circuitry is provided to record a set indicator corresponding to a target physical address, where the set indicator depends on which set of one or more storage locations of the cache corresponds to the target physical address. The set indicator is insufficient to identify the target physical address itself. This enables performance issues caused by contention of data items for individual sets in a physically-indexed set-associative or direct-mapped cache to be identified without needing to expose the physical address itself to potentially insecure processes or devices.