Reduce NVSHMEM gpu memory usage and disable MNNVL. (#190)

Co-authored-by: Shangyan Zhou <sy.zhou@deepseek.com>

deep_ep/buffer.py

@@ -79,9 +79,18 @@ class Buffer:
             os.environ['NVSHMEM_IBGDA_NUM_RC_PER_PE'] = f'{num_qps_per_rank}'
             # Make sure QP depth is always larger than the number of on-flight WRs, so that we can skip WQ slot check
             os.environ['NVSHMEM_QP_DEPTH'] = '1024'
+
+            # Reduce gpu memory usage
+            # 6 default teams + 1 extra team
+            os.environ['NVSHMEM_MAX_TEAMS'] = '7'
+            # Disable NVLink SHArP
+            os.environ['NVSHMEM_DISABLE_NVLS'] = '1'
             # NOTES: NVSHMEM initialization requires at least 256 MiB
             os.environ['NVSHMEM_CUMEM_GRANULARITY'] = f'{2 ** 29}'
 
+            # Disable multi-node NVLink detection
+            os.environ['NVSHMEM_DISABLE_MNNVL'] = '1'
+
             # Synchronize using the root ID
             nvshmem_unique_ids = [None, ] * self.group_size
             if (low_latency_mode and self.rank == 0) or (not low_latency_mode and self.runtime.get_rdma_rank() == 0):