libcapulet: use 4096-byte MTU

libcapulet/rdma_ib.c

@@ -146,11 +146,12 @@ bool capulet_rdma_ib_set_peer_from_udp(struct CapuletRdmaIbContext *ctx, struct
 	// Change state from Init to RTR (Ready To Receive)
 	memset(&ibv_dev_qp_params, 0, sizeof(struct ibv_qp_attr));
 	ibv_dev_qp_params.qp_state = IBV_QPS_RTR;
-	ibv_dev_qp_params.path_mtu = IBV_MTU_1024;
+	ibv_dev_qp_params.path_mtu = IBV_MTU_4096;
 	ibv_dev_qp_params.dest_qp_num = udp_ctx->remote->qpn;
 	ibv_dev_qp_params.rq_psn = udp_ctx->remote->psn;
 	ibv_dev_qp_params.max_dest_rd_atomic = 1;
-	ibv_dev_qp_params.min_rnr_timer = 12;
+	// 0xd = 960 μs delay
+	ibv_dev_qp_params.min_rnr_timer = 0xd;
 
 	ibv_dev_qp_params.ah_attr.is_global = 1;
 	ibv_dev_qp_params.ah_attr.dlid = udp_ctx->remote->lid;