From 093279cd028299b771a96dea30fd8d193b2e1d80 Mon Sep 17 00:00:00 2001
From: Quentin Young <qlyoung@cumulusnetworks.com>
Date: Fri, 4 Oct 2019 18:52:24 +0000
Subject: [PATCH] bgpd: vector I/O

Signed-off-by: Quentin Young <qlyoung@cumulusnetworks.com>
---
 bgpd/bgp_io.c | 101 +++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 80 insertions(+), 21 deletions(-)

diff --git a/bgpd/bgp_io.c b/bgpd/bgp_io.c
index c8b7e5155f..c4555afc52 100644
--- a/bgpd/bgp_io.c
+++ b/bgpd/bgp_io.c
@@ -22,6 +22,7 @@
 /* clang-format off */
 #include <zebra.h>
 #include <pthread.h>		// for pthread_mutex_unlock, pthread_mutex_lock
+#include <sys/uio.h>		// for writev
 
 #include "frr_pthread.h"
 #include "linklist.h"		// for list_delete, list_delete_all_node, lis...
@@ -275,35 +276,94 @@ static uint16_t bgp_write(struct peer *peer)
 {
 	uint8_t type;
 	struct stream *s;
-	int num;
 	int update_last_write = 0;
-	unsigned int count = 0;
+	unsigned int count;
 	uint32_t uo = 0;
 	uint16_t status = 0;
 	uint32_t wpkt_quanta_old;
 
+	int writenum = 0;
+	int num;
+	unsigned int iovsz;
+	unsigned int strmsz;
+	unsigned int total_written;
+
 	wpkt_quanta_old = atomic_load_explicit(&peer->bgp->wpkt_quanta,
 					       memory_order_relaxed);
+	struct stream *ostreams[wpkt_quanta_old];
+	struct stream **streams = ostreams;
+	struct iovec iov[wpkt_quanta_old];
+
+	s = stream_fifo_head(peer->obuf);
+
+	if (!s)
+		goto done;
+
+	count = iovsz = 0;
+	while (count < wpkt_quanta_old && iovsz < array_size(iov) && s) {
+		ostreams[iovsz] = s;
+		iov[iovsz].iov_base = stream_pnt(s);
+		iov[iovsz].iov_len = STREAM_READABLE(s);
+		writenum += STREAM_READABLE(s);
+		s = s->next;
+		++iovsz;
+		++count;
+	}
+
+	strmsz = iovsz;
+	total_written = 0;
+
+	do {
+		num = writev(peer->fd, iov, iovsz);
+
+		if (num < 0) {
+			if (!ERRNO_IO_RETRY(errno)) {
+				BGP_EVENT_ADD(peer, TCP_fatal_error);
+				SET_FLAG(status, BGP_IO_FATAL_ERR);
+			} else {
+				SET_FLAG(status, BGP_IO_TRANS_ERR);
+			}
+
+			break;
+		} else if (num != writenum) {
+			unsigned int msg_written = 0;
+			unsigned int ic = iovsz;
+
+			for (unsigned int i = 0; i < ic; i++) {
+				size_t ss = iov[i].iov_len;
 
-	while (count < wpkt_quanta_old && (s = stream_fifo_head(peer->obuf))) {
-		int writenum;
-		do {
-			writenum = stream_get_endp(s) - stream_get_getp(s);
-			num = write(peer->fd, stream_pnt(s), writenum);
+				if (ss > (unsigned int) num)
+					break;
 
-			if (num < 0) {
-				if (!ERRNO_IO_RETRY(errno)) {
-					BGP_EVENT_ADD(peer, TCP_fatal_error);
-					SET_FLAG(status, BGP_IO_FATAL_ERR);
-				} else {
-					SET_FLAG(status, BGP_IO_TRANS_ERR);
-				}
+				msg_written++;
+				iovsz--;
+				writenum -= ss;
+				num -= ss;
+			}
 
-				goto done;
-			} else if (num != writenum)
-				stream_forward_getp(s, num);
+			total_written += msg_written;
 
-		} while (num != writenum);
+			memmove(&iov, &iov[msg_written],
+				sizeof(iov[0]) * iovsz);
+			streams = &streams[msg_written];
+			stream_forward_getp(streams[0], num);
+			iov[0].iov_base = stream_pnt(streams[0]);
+			iov[0].iov_len = STREAM_READABLE(streams[0]);
+
+			writenum -= num;
+			num = 0;
+			assert(writenum > 0);
+		} else {
+			total_written = strmsz;
+		}
+
+	} while (num != writenum);
+
+	/* Handle statistics */
+	for (unsigned int i = 0; i < total_written; i++) {
+		s = stream_fifo_pop(peer->obuf);
+
+		assert(s == ostreams[i]);
 
 		/* Retrieve BGP packet type. */
 		stream_set_getp(s, BGP_MARKER_SIZE + 2);
@@ -351,9 +411,8 @@ static uint16_t bgp_write(struct peer *peer)
 			break;
 		}
 
-		count++;
-
-		stream_free(stream_fifo_pop(peer->obuf));
+		stream_free(s);
+		ostreams[i] = NULL;
 		update_last_write = 1;
 	}
 
-- 
2.39.5