Method and apparatus for filtering memory write snoop activity in a distributed shared memory computer

Abstract

A method and apparatus for filtering memory probe activity for writes in a distributed shared memory computer. In one embodiment, the method may include initiating a first store operation to a cache data block stored in a first cache from a first processing node and initiating a first load operation to said cache data block from a second processing node subsequent to initiating said first store operation; and assigning a pairwise-shared directory state to a coherence directory entry corresponding to said cache data block in response to initiating said first load operation. The method may further include initiating a second store operation to said cache data block from said second processing node subsequent to initiating said first load operation; and assigning a migratory directory state to said coherence directory entry in response to initiating said second store operation, where the migratory directory state is distinct from a modified directory state.