MEDIUM/OPTIM: mux-quic: define a recv_list for demux resumption

This commit is part of the current serie which aims to refactor and
improve overall performance of QUIC MUX I/O handler.

Define a recv_list element into qcc structure. This is used to
registered every instance of qcs which are currently blocked on
demuxing, which happen on no more space in <rx.appbuf>.

The purpose of this patch is to reduce qcc_io_recv() CPU usage. Now,
only recv_list iteration is performed, instead of the previous looping
over every qcs instances. This is useful as qcc_io_recv() is called each
time qcc_io_cb() is scheduled, even if only sending condition was the
wakeup origin.

A qcs is not inserted into recv_list immediately after blocking on demux
full buffer. Instead, this is only done after unblocking via stream
rcv_buf callback, which ensure that new buffer space is available.

This should be backported up to 3.1.

include/haproxy/mux_quic-t.h

@@ -82,6 +82,7 @@ struct qcc {
 
 	struct eb_root streams_by_id; /* all active streams by their ID */
 
+	struct list recv_list; /* list of qcs for which demux can be resumed */
 	struct list send_list; /* list of qcs ready to send (STREAM, STOP_SENDING or RESET_STREAM emission) */
 	struct list fctl_list; /* list of sending qcs blocked on conn flow control */
 	struct list buf_wait_list; /* list of qcs blocked on stream desc buf */
@@ -150,6 +151,7 @@ struct qcs {
 	uint64_t id;
 	struct qc_stream_desc *stream;
 
+	struct list el_recv; /* element of qcc.recv_list */
 	struct list el_send; /* element of qcc.send_list */
 	struct list el_opening; /* element of qcc.opening_list */
 	struct list el_fctl; /* element of qcc.fctl_list */

src/mux_quic.c

@@ -85,6 +85,7 @@ static void qcs_free(struct qcs *qcs)
 
 	/* Safe to use even if already removed from the list. */
 	LIST_DEL_INIT(&qcs->el_opening);
+	LIST_DEL_INIT(&qcs->el_recv);
 	LIST_DEL_INIT(&qcs->el_send);
 	LIST_DEL_INIT(&qcs->el_fctl);
 	LIST_DEL_INIT(&qcs->el_buf);
@@ -138,6 +139,7 @@ static struct qcs *qcs_new(struct qcc *qcc, uint64_t id, enum qcs_type type)
 	 * These fields must be initialed before.
 	 */
 	LIST_INIT(&qcs->el_opening);
+	LIST_INIT(&qcs->el_recv);
 	LIST_INIT(&qcs->el_send);
 	LIST_INIT(&qcs->el_fctl);
 	LIST_INIT(&qcs->el_buf);
@@ -1605,6 +1607,7 @@ int qcc_recv(struct qcc *qcc, uint64_t id, uint64_t len, uint64_t offset,
 
 	if ((ncb_data(&qcs->rx.ncbuf, 0) && !(qcs->flags & QC_SF_DEM_FULL)) || fin) {
 		qcc_decode_qcs(qcc, qcs);
+		LIST_DEL_INIT(&qcs->el_recv);
 		qcc_refresh_timeout(qcc);
 	}
 
@@ -2509,14 +2512,13 @@ static void qcc_wait_for_hs(struct qcc *qcc)
 	TRACE_LEAVE(QMUX_EV_QCC_RECV, qcc->conn);
 }
 
-/* Proceed on receiving. Loop through all streams from <qcc> and use decode_qcs
+/* Proceed on receiving. Loop on streams subscribed in recv_list and performed
- * operation.
+ * STREAM frames decoding upon them.
  *
  * Returns 0 on success else non-zero.
  */
 static int qcc_io_recv(struct qcc *qcc)
 {
-	struct eb64_node *node;
 	struct qcs *qcs;
 
 	TRACE_ENTER(QMUX_EV_QCC_RECV, qcc->conn);
@@ -2530,25 +2532,12 @@ static int qcc_io_recv(struct qcc *qcc)
 	if ((qcc->flags & QC_CF_WAIT_HS) && !(qcc->wait_event.events & SUB_RETRY_RECV))
 		qcc_wait_for_hs(qcc);
 
-	node = eb64_first(&qcc->streams_by_id);
+	while (!LIST_ISEMPTY(&qcc->recv_list)) {
-	while (node) {
+		qcs = LIST_ELEM(qcc->recv_list.n, struct qcs *, el_recv);
-		uint64_t id;
+		/* No need to add an uni local stream in recv_list. */
-
+		BUG_ON(quic_stream_is_uni(qcs->id) && quic_stream_is_local(qcc, qcs->id));
-		qcs = eb64_entry(node, struct qcs, by_id);
-		id = qcs->id;
-
-		if (!ncb_data(&qcs->rx.ncbuf, 0) || (qcs->flags & QC_SF_DEM_FULL)) {
-			node = eb64_next(node);
-			continue;
-		}
-
-		if (quic_stream_is_uni(id) && quic_stream_is_local(qcc, id)) {
-			node = eb64_next(node);
-			continue;
-		}
-
 		qcc_decode_qcs(qcc, qcs);
-		node = eb64_next(node);
+		LIST_DEL_INIT(&qcs->el_recv);
 	}
 
 	TRACE_LEAVE(QMUX_EV_QCC_RECV, qcc->conn);
@@ -2998,6 +2987,7 @@ static int qmux_init(struct connection *conn, struct proxy *prx,
 		goto err;
 	}
 
+	LIST_INIT(&qcc->recv_list);
 	LIST_INIT(&qcc->send_list);
 	LIST_INIT(&qcc->fctl_list);
 	LIST_INIT(&qcc->buf_wait_list);
@@ -3213,9 +3203,11 @@ static size_t qmux_strm_rcv_buf(struct stconn *sc, struct buffer *buf,
 		BUG_ON(!ncb_data(&qcs->rx.ncbuf, 0));
 
 		qcs->flags &= ~QC_SF_DEM_FULL;
-		if (!(qcc->flags & QC_CF_ERRL))
+		if (!(qcc->flags & QC_CF_ERRL)) {
+			LIST_APPEND(&qcc->recv_list, &qcs->el_recv);
 			qcc_wakeup(qcc);
 		}
+	}
 
 	TRACE_LEAVE(QMUX_EV_STRM_RECV, qcc->conn, qcs);