Recovering data segment contents in a distributed shared memory

摘要

Systems and methods for implementing a distributed shared memory (DSM) in a computer cluster in which an unreliable underlying message passing technology is used, such that the DSM efficiently maintains coherency and reliability. DSM agents residing on different nodes of the cluster process access permission requests of local and remote users on specified data segments via handling procedures, which provide for recovering of lost ownership of a data segment while ensuring exclusive ownership of a data segment among the DSM agents detecting and resolving a no-owner messaging deadlock, pruning of obsolete messages, and recovery of the latest contents of a data segment whose ownership has been lost.

主权项

1. A method for recovering data segment contents in a distributed shared memory (DSM) using a processor device, comprising:
upon losing ownership of a data segment, processing a permission request for a first one of a plurality of distributed shared memory (DSM) agents that is sent from a second one of the plurality of DSM agents for the data segment which the first one of the plurality of DSM agents maintains as owned by the second one of the plurality of DSM agents; and determining, by the first one of the plurality of DSM agents, that the data segment contents of the data segment, that is requested, are most recent data segment contents, wherein if the data segment contents of the data segment that are requested are identified as the most recent data segment contents, the data segment is restored, wherein data segment contents are the most recent data segment contents if:
the first one of the plurality of DSM agents has a valid access permission on the data segment, orthe first one of the plurality of DSM agents does not have a valid permission on the data segment and the local value of first one of the plurality of DSM agents for the data segment version is more recent that the value of the data segment version in the permission request received from the second one of the plurality of DSM agents.