RDS: IB: ack more receive completions to improve performance

For better performance, we split the receive completion IRQ handler. That
lets us acknowledge several WCE events in one call. We also limit the WC
to max 32 to avoid latency. Acknowledging several completions in one call
instead of several calls each time will provide better performance since
less mutual exclusion locks are being performed.

In next patch, send completion is also split which re-uses the poll_cq()
and hence the code is moved to ib_cm.c

Signed-off-by: Santosh Shilimkar <ssantosh@kernel.org>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>

1 files changed, 37 insertions, 99 deletions

diff --git a/net/rds/ib_recv.c b/net/rds/ib_recv.c
index f43831e4186a..96744b75db93 100644
--- a/net/rds/ib_recv.c
+++ b/net/rds/ib_recv.c
@@ -596,8 +596,7 @@ void rds_ib_recv_init_ack(struct rds_ib_connection *ic)
  * wr_id and avoids working with the ring in that case.
  */
 #ifndef KERNEL_HAS_ATOMIC64
-static void rds_ib_set_ack(struct rds_ib_connection *ic, u64 seq,
-				int ack_required)
+void rds_ib_set_ack(struct rds_ib_connection *ic, u64 seq, int ack_required)
 {
 	unsigned long flags;
 
@@ -622,8 +621,7 @@ static u64 rds_ib_get_ack(struct rds_ib_connection *ic)
 	return seq;
 }
 #else
-static void rds_ib_set_ack(struct rds_ib_connection *ic, u64 seq,
-				int ack_required)
+void rds_ib_set_ack(struct rds_ib_connection *ic, u64 seq, int ack_required)
 {
 	atomic64_set(&ic->i_ack_next, seq);
 	if (ack_required) {
@@ -830,20 +828,6 @@ static void rds_ib_cong_recv(struct rds_connection *conn,
 	rds_cong_map_updated(map, uncongested);
 }
 
-/*
- * Rings are posted with all the allocations they'll need to queue the
- * incoming message to the receiving socket so this can't fail.
- * All fragments start with a header, so we can make sure we're not receiving
- * garbage, and we can tell a small 8 byte fragment from an ACK frame.
- */
-struct rds_ib_ack_state {
-	u64		ack_next;
-	u64		ack_recv;
-	unsigned int	ack_required:1;
-	unsigned int	ack_next_valid:1;
-	unsigned int	ack_recv_valid:1;
-};
-
 static void rds_ib_process_recv(struct rds_connection *conn,
 				struct rds_ib_recv_work *recv, u32 data_len,
 				struct rds_ib_ack_state *state)
@@ -969,96 +953,50 @@ static void rds_ib_process_recv(struct rds_connection *conn,
 	}
 }
 
-/*
- * Plucking the oldest entry from the ring can be done concurrently with
- * the thread refilling the ring.  Each ring operation is protected by
- * spinlocks and the transient state of refilling doesn't change the
- * recording of which entry is oldest.
- *
- * This relies on IB only calling one cq comp_handler for each cq so that
- * there will only be one caller of rds_recv_incoming() per RDS connection.
- */
-void rds_ib_recv_cq_comp_handler(struct ib_cq *cq, void *context)
-{
-	struct rds_connection *conn = context;
-	struct rds_ib_connection *ic = conn->c_transport_data;
-
-	rdsdebug("conn %p cq %p\n", conn, cq);
-
-	rds_ib_stats_inc(s_ib_rx_cq_call);
-
-	tasklet_schedule(&ic->i_recv_tasklet);
-}
-
-static inline void rds_poll_cq(struct rds_ib_connection *ic,
-			       struct rds_ib_ack_state *state)
+void rds_ib_recv_cqe_handler(struct rds_ib_connection *ic,
+			     struct ib_wc *wc,
+			     struct rds_ib_ack_state *state)
 {
 	struct rds_connection *conn = ic->conn;
-	struct ib_wc wc;
 	struct rds_ib_recv_work *recv;
 
-	while (ib_poll_cq(ic->i_recv_cq, 1, &wc) > 0) {
-		rdsdebug("wc wr_id 0x%llx status %u (%s) byte_len %u imm_data %u\n",
-			 (unsigned long long)wc.wr_id, wc.status,
-			 ib_wc_status_msg(wc.status), wc.byte_len,
-			 be32_to_cpu(wc.ex.imm_data));
-		rds_ib_stats_inc(s_ib_rx_cq_event);
+	rdsdebug("wc wr_id 0x%llx status %u (%s) byte_len %u imm_data %u\n",
+		 (unsigned long long)wc->wr_id, wc->status,
+		 ib_wc_status_msg(wc->status), wc->byte_len,
+		 be32_to_cpu(wc->ex.imm_data));
 
-		recv = &ic->i_recvs[rds_ib_ring_oldest(&ic->i_recv_ring)];
-
-		ib_dma_unmap_sg(ic->i_cm_id->device, &recv->r_frag->f_sg, 1, DMA_FROM_DEVICE);
-
-		/*
-		 * Also process recvs in connecting state because it is possible
-		 * to get a recv completion _before_ the rdmacm ESTABLISHED
-		 * event is processed.
-		 */
-		if (wc.status == IB_WC_SUCCESS) {
-			rds_ib_process_recv(conn, recv, wc.byte_len, state);
-		} else {
-			/* We expect errors as the qp is drained during shutdown */
-			if (rds_conn_up(conn) || rds_conn_connecting(conn))
-				rds_ib_conn_error(conn, "recv completion on %pI4 had "
-						  "status %u (%s), disconnecting and "
-						  "reconnecting\n", &conn->c_faddr,
-						  wc.status,
-						  ib_wc_status_msg(wc.status));
-		}
+	rds_ib_stats_inc(s_ib_rx_cq_event);
+	recv = &ic->i_recvs[rds_ib_ring_oldest(&ic->i_recv_ring)];
+	ib_dma_unmap_sg(ic->i_cm_id->device, &recv->r_frag->f_sg, 1,
+			DMA_FROM_DEVICE);
 
-		/*
-		 * rds_ib_process_recv() doesn't always consume the frag, and
-		 * we might not have called it at all if the wc didn't indicate
-		 * success. We already unmapped the frag's pages, though, and
-		 * the following rds_ib_ring_free() call tells the refill path
-		 * that it will not find an allocated frag here. Make sure we
-		 * keep that promise by freeing a frag that's still on the ring.
-		 */
-		if (recv->r_frag) {
-			rds_ib_frag_free(ic, recv->r_frag);
-			recv->r_frag = NULL;
-		}
-		rds_ib_ring_free(&ic->i_recv_ring, 1);
+	/* Also process recvs in connecting state because it is possible
+	 * to get a recv completion _before_ the rdmacm ESTABLISHED
+	 * event is processed.
+	 */
+	if (wc->status == IB_WC_SUCCESS) {
+		rds_ib_process_recv(conn, recv, wc->byte_len, state);
+	} else {
+		/* We expect errors as the qp is drained during shutdown */
+		if (rds_conn_up(conn) || rds_conn_connecting(conn))
+			rds_ib_conn_error(conn, "recv completion on %pI4 had status %u (%s), disconnecting and reconnecting\n",
+					  &conn->c_faddr,
+					  wc->status,
+					  ib_wc_status_msg(wc->status));
 	}
-}
 
-void rds_ib_recv_tasklet_fn(unsigned long data)
-{
-	struct rds_ib_connection *ic = (struct rds_ib_connection *) data;
-	struct rds_connection *conn = ic->conn;
-	struct rds_ib_ack_state state = { 0, };
-
-	rds_poll_cq(ic, &state);
-	ib_req_notify_cq(ic->i_recv_cq, IB_CQ_SOLICITED);
-	rds_poll_cq(ic, &state);
-
-	if (state.ack_next_valid)
-		rds_ib_set_ack(ic, state.ack_next, state.ack_required);
-	if (state.ack_recv_valid && state.ack_recv > ic->i_ack_recv) {
-		rds_send_drop_acked(conn, state.ack_recv, NULL);
-		ic->i_ack_recv = state.ack_recv;
+	/* rds_ib_process_recv() doesn't always consume the frag, and
+	 * we might not have called it at all if the wc didn't indicate
+	 * success. We already unmapped the frag's pages, though, and
+	 * the following rds_ib_ring_free() call tells the refill path
+	 * that it will not find an allocated frag here. Make sure we
+	 * keep that promise by freeing a frag that's still on the ring.
+	 */
+	if (recv->r_frag) {
+		rds_ib_frag_free(ic, recv->r_frag);
+		recv->r_frag = NULL;
 	}
-	if (rds_conn_up(conn))
-		rds_ib_attempt_ack(ic);
+	rds_ib_ring_free(&ic->i_recv_ring, 1);
 
 	/* If we ever end up with a really empty receive ring, we're
 	 * in deep trouble, as the sender will definitely see RNR