A technique of identifying IO hot spots is performed in a data storage apparatus (e.g., a file server). The technique involves updating, in response to host IO operations which lock ranges of extents prior to accessing the ranges of extents, contents of a lock history database based on the ranges of extents which were locked by the host IO operations. The technique further involves receiving a lock history request. The technique further involves providing, in response to the lock history request, the contents of the lock history database to identify, as the IO hot spots, extents which were locked by the host IO operations.