Update hwloc CPU Binding Implementation#1226
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…policies
Removes the HWLOC_ENFORCE_SINGLE_SOCKET / HWLOC_ENFORCE_SINGLE_NUMA_NODE
compile-time flags that unconditionally narrowed each PE's CPU affinity
mask at startup, overriding any binding set by the job launcher.
Replaces them with SHMEM_CPU_PLACEMENT_POLICY (default: none), a runtime
env var that lets users opt in to a specific placement strategy:
none - no changes; launcher owns CPU affinity entirely (default)
best-memory - bind CPUs to the NUMA node of the PE's current location
numa-local - alias for best-memory
socket-local - bind CPUs to the socket of the PE's current location
balanced-numa - round-robin PEs across NUMA nodes by local rank;
also sets memory binding via hwloc_set_membind
best-network - bind CPUs to the NUMA domain of the assigned NIC;
applied in transport_ofi.c after NIC selection
Adds SHMEM_DISABLE_CPU_BINDING (bool, default false) to suppress all
hwloc CPU placement regardless of policy.
The best-network policy is implemented in assign_nic_with_hwloc() in
transport_ofi.c, where the selected NIC's PCI bus attributes are already
in scope. All other policies are applied in a new apply_cpu_placement()
helper in init.c, called after hwloc_topology_load().
The hwloc topology object is preserved as it is still required by NIC
affinity selection in transport_ofi.c.
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Problem
This PR replaces the previous compile-time-gated hwloc CPU binding in
shmem_internal_heap_postinit()Solution
Replace it with an opt-in system controlled by the new
SHMEM_CPU_PLACEMENT_POLICYenvironment variable (default:none).Available policies:
none(default)best-memory/numa-localsocket-localbalanced-numahwloc_set_membindbest-networkassign_nic_with_hwloc()after NIC selectionSHMEM_DISABLE_CPU_BINDING=truesuppresses all placement regardless of policy. The hwloc topologyinitialization is preserved as it is still required by NIC affinity selection in
transport_ofi.c.Files changed
src/init.c— removed old rebind logic; addedapply_cpu_placement()dispatching on policy namesrc/shmem_env_defs.h— addedSHMEM_CPU_PLACEMENT_POLICYenv var; updatedSHMEM_DISABLE_CPU_BINDINGdescriptionsrc/transport_ofi.c— addedbest-networkpolicy insideassign_nic_with_hwloc()where PCI topology is already in scopeTest coverage