Allocating a global shared memory

A data processing system, comprising:

• an interconnect fabric;
• and
• a plurality of nodes coupled to the interconnect fabric, at least one of the plurality of nodes including data storage containing global system memory (GSM) program code executable within multiple of the plurality of nodes as a parallel job including multiple tasks, wherein when said GSM program code is executed, each of the multiple tasks issues a system call to request allocation of backing storage in physical memory for global shared memory accessible to all of the multiple tasks within the parallel job, wherein said global shared memory is in a global address space defined by a range of effective addresses;
• wherein each task among the multiple tasks receives an indication that the allocation requested by the system call was successful only if the global address space for that task was previously reserved and backing storage for the global shared memory has not already been allocated.

A program product, comprising:

• a data storage medium readable by a data processing system having a plurality of nodes coupled by an interconnect fabric;
• and
• global system memory (GSM) program code within the data storage medium that is executable by the data processing system within multiple of the plurality of nodes as a parallel job including multiple tasks, wherein when said GSM program code is executed, each of the multiple tasks issues a system call to request allocation of backing storage in physical memory for global shared memory accessible to all of the multiple tasks within the parallel job, wherein said global shared memory is in a global address space defined by a range of effective addresses;
• wherein each task among the multiple tasks receives an indication that the allocation requested by the system call was successful only if the global address space for that task was previously reserved and backing storage for the global shared memory has not already been allocated.