Using ephemeral stores for fine-grained conflict detection in a hardware accelerated stm

Abstract

A method and apparatus for fine-grained filtering in a hardware accelerated software transactional memory system is herein described. A data object, which may have an arbitrary size, is associated with a filter word. The filter word is in a first default state when no access, such as a read, from the data object has occurred during a pendancy of a transaction. Upon encountering a first access, such as a first read, from the data object, access barrier operations including an ephemeral/private store operation to set the filter word to a second state are performed. Upon a subsequent/redundant access, such as a second read, the access barrier operations are elided to accelerate the subsequent access, based on the filter word being set to the second state to indicate a previous access occurred.