A method of transferring data between two caches comprises sending a first message from a first processor to a second processor indicating that data is available for transfer from a first cache associated with the first processor, requesting, from the second processor, a data transfer of the data from the first cache to a second cache associated with the second processor, transferring the data from the first cache to the second cache in response to the request, and sending a second message from the second processor to the first processor indicating that the data transfer is complete.