Reduce LL threshold for a2a (#2032)

[ROCm/rccl commit: 52f9526bd6]

projects/rccl/src/enqueue.cc

@@ -928,7 +928,7 @@ static ncclResult_t scheduleCollTasksToPlan(
   return ncclSuccess;
 }
 
-NCCL_PARAM(P2pLLThreshold, "P2P_LL_THRESHOLD", 16384);
+NCCL_PARAM(P2pLLThreshold, "P2P_LL_THRESHOLD", 8192);
 RCCL_PARAM(P2pNetThreshold, "P2P_NET_THRESHOLD", 131072);
 NCCL_PARAM(ChunkSize, "CHUNK_SIZE", 0);