Fix CPU and memory affinity under external resource management

- Fixes CPU affinity when running inference on CPU, and when CPUs
  are externally managed using taskset, numactl, cgroups, Kubernetes
  CPU manager, NRI resource policy plugins, for instance.

- Detect external CPU management and trust the external CPU manager
  completely. It is more likely that external manager has the big picture
  of all other tasks running on the system, their QoS, hardware
  characteristics, etc.

- For instance, do not modify even memory affinity, because the external
  manager may know better which NUMA node has fastest memory, or which
  NUMA nodes have enough free memory for this inference.

Fixes: #3011

Signed-off-by: Antti Kervinen <antti.kervinen@intel.com>

server/text_generation_server/models/flash_causal_lm.py

@@ -102,6 +102,39 @@ def get_sliding_windows() -> int:
 
 
 def init_cpu_threads_env(rank_id: int, world_size: int):
+    import psutil
+    allowed_cpus = psutil.Process().cpu_affinity()
+    if len(allowed_cpus) < psutil.cpu_count(logical=True):
+        _init_cpu_threads_env_use_allowed(rank_id, world_size, allowed_cpus)
+    else:
+        _init_cpu_threads_env_use_all(rank_id, world_size)
+
+def _init_cpu_threads_env_use_allowed(rank_id: int, world_size: int, allowed_cpus: list):
+    import importlib.util
+
+    if os.getenv("OMP_NUM_THREADS") is None:
+        num_cpus_per_rank = max(int(len(allowed_cpus) / world_size), 1)
+    else:
+        num_cpus_per_rank = min(int(os.getenv("OMP_NUM_THREADS")), len(allowed_cpus))
+
+    if importlib.util.find_spec("numa") is not None:
+        import numa
+
+        slice_info = f"slice {rank_id+1}/{world_size} of externally allowed {len(allowed_cpus)} CPUs"
+        allowed_mems = numa.memory.get_membind_nodes()
+        cpu_start = num_cpus_per_rank * rank_id
+        allowed_cpus_for_rank = allowed_cpus[cpu_start : cpu_start + num_cpus_per_rank]
+        numa.schedule.run_on_cpus(0, *allowed_cpus_for_rank)
+        effective_allowed_cpus = numa.schedule.get_affinitive_cpus(0)
+    else:
+        slice_info = "externally allowed, cannot import numa for slicing"
+        allowed_mems = "n/a"
+        effective_allowed_cpus = allowed_cpus
+    num_threads = num_cpus_per_rank
+    torch.set_num_threads(num_threads)
+    logger.info(f"affinity={effective_allowed_cpus} ({slice_info}), membind={allowed_mems}, threads={num_threads}")
+
+def _init_cpu_threads_env_use_all(rank_id: int, world_size: int):
     import importlib.util
 
     if importlib.util.find_spec("numa") is not None: