RDMA/rtrs-srv: Set minimal max_send_wr and max_recv_wr

Currently rtrs when create_qp use a coarse numbers (bigger in general),
which leads to hardware create more resources which only waste memory with
no benefits.

For max_send_wr, we don't really need alway max_qp_wr size when creating
qp, reduce it to cq_size.

For max_recv_wr,  cq_size is enough.

With the patch when sess_queue_depth=128, per session (2 paths) memory
consumption reduced from 188 MB to 65MB

When always_invalidate is enabled, we need send more wr, so treat it
special.

Fixes: 9cb8374804 ("RDMA/rtrs: server: main functionality")
Link: https://lore.kernel.org/r/20210614090337.29557-2-jinpu.wang@ionos.com
Signed-off-by: Jack Wang <jinpu.wang@cloud.ionos.com>
Reviewed-by: Md Haris Iqbal <haris.iqbal@cloud.ionos.com>
Signed-off-by: Gioh Kim <gi-oh.kim@ionos.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/infiniband/ulp/rtrs/rtrs-srv.c

@@ -1634,7 +1634,7 @@ static int create_con(struct rtrs_srv_sess *sess,
 	struct rtrs_sess *s = &sess->s;
 	struct rtrs_srv_con *con;
 
-	u32 cq_size, wr_queue_size;
+	u32 cq_size, max_send_wr, max_recv_wr, wr_limit;
 	int err, cq_vector;
 
 	con = kzalloc(sizeof(*con), GFP_KERNEL);
@@ -1655,30 +1655,42 @@ static int create_con(struct rtrs_srv_sess *sess,
 		 * All receive and all send (each requiring invalidate)
 		 * + 2 for drain and heartbeat
 		 */
-		wr_queue_size = SERVICE_CON_QUEUE_DEPTH * 3 + 2;
-		cq_size = wr_queue_size;
+		max_send_wr = SERVICE_CON_QUEUE_DEPTH * 2 + 2;
+		max_recv_wr = SERVICE_CON_QUEUE_DEPTH + 2;
+		cq_size = max_send_wr + max_recv_wr;
 	} else {
-		/*
-		 * If we have all receive requests posted and
-		 * all write requests posted and each read request
-		 * requires an invalidate request + drain
-		 * and qp gets into error state.
-		 */
-		cq_size = srv->queue_depth * 3 + 1;
 		/*
 		 * In theory we might have queue_depth * 32
 		 * outstanding requests if an unsafe global key is used
 		 * and we have queue_depth read requests each consisting
 		 * of 32 different addresses. div 3 for mlx5.
 		 */
-		wr_queue_size = sess->s.dev->ib_dev->attrs.max_qp_wr / 3;
+		wr_limit = sess->s.dev->ib_dev->attrs.max_qp_wr / 3;
+		/* when always_invlaidate enalbed, we need linv+rinv+mr+imm */
+		if (always_invalidate)
+			max_send_wr =
+				min_t(int, wr_limit,
+				      srv->queue_depth * (1 + 4) + 1);
+		else
+			max_send_wr =
+				min_t(int, wr_limit,
+				      srv->queue_depth * (1 + 2) + 1);
+
+		max_recv_wr = srv->queue_depth + 1;
+		/*
+		 * If we have all receive requests posted and
+		 * all write requests posted and each read request
+		 * requires an invalidate request + drain
+		 * and qp gets into error state.
+		 */
+		cq_size = max_send_wr + max_recv_wr;
 	}
-	atomic_set(&con->sq_wr_avail, wr_queue_size);
+	atomic_set(&con->sq_wr_avail, max_send_wr);
 	cq_vector = rtrs_srv_get_next_cq_vector(sess);
 
 	/* TODO: SOFTIRQ can be faster, but be careful with softirq context */
 	err = rtrs_cq_qp_create(&sess->s, &con->c, 1, cq_vector, cq_size,
-				 wr_queue_size, wr_queue_size,
+				 max_send_wr, max_recv_wr,
 				 IB_POLL_WORKQUEUE);
 	if (err) {
 		rtrs_err(s, "rtrs_cq_qp_create(), err: %d\n", err);