1. A data processing system comprising: a processing unit executing a first task of a parallel job; a local memory and a memory controller controlling access to the local memory; and a host fabric interface (HFI) including: processing logic for completing a plurality of operations that enable parallel job execution via a plurality of distributed tasks that have a global shared memory (GSM) accessible by a grouping of effective addresses (EAs), wherein only a first portion of effective addresses within a global address space (GAS) is mapped to the local memory, while other portions of the GAS are mapped to other physical memory of other nodes within a GSM environment; and a first HFI window assigned to the first task, wherein said first HFI window processes send operations generated from commands issued by the first task and processes received GSM operations that include an effective address (EA), which corresponds to an EA of the first task and which maps to a real address (RA) of the first task within the local memory; wherein said local memory includes one or more physical locations to which effective addresses of the task executing on the processor are mapped; and wherein the processing logic for completing the plurality of operations comprises processing logic for: assigning the one or more physical locations within the local memory to the first task executing on the local node, said assigning one or more physical locations including: assigning a send FIFO (first-in first-out buffer) in which commands issued by the first task are stored, while said commands are awaiting processing by the HFI; and assigning a receive FIFO for holding operations and data received from the network fabric at the HFI window assigned to the first task, which operations and data include EAs with RAs that are mapped to a portion of local memory assigned to the first task's EA; storing within the send FIFO one or more commands generated by the first task, wherein the first task generates the one or more commands as GSM commands and places the one or more commands into the send FIFO from which the commands are later retrieved for processing by the HFI; determining when HFI resources are available to allocate for processing a GSM command of the first task; in response to HFI resources being available to allocate for processing the GSM command, retrieving the GSM command from the send FIFO; generating a GSM packet from the retrieved GSM command at the HFI window assigned to the first task; embedding task and HFI window identifying information with a generated GSM packet; tagging the GSM packet with a job ID of the parallel job to which the first task and second task belongs; and issuing the GSM packet out on the network fabric for routing to the destination node identified within the GSM packet; and wherein the first HFI window rejects a received GSM packet whose operations and/or data are not associated with EAs for which EA-to-RA translations exist to the local physical memory, wherein said local memory includes the one or more physical locations to which EAs of the first task executing on the processor of the local node are mapped.