netmap: pkt-gen: init all slots of every tx ring

sender_body() uses OPT_COPY to copy the frame into the destination slot
for the first 100,000 packets. Then it removes OPT_COPY to improve
performance. The function always starts with the first tx ring.

If multiple tx rings are in use, it is possible that the initial 100k
packets will only use the first ring. After OPT_COPY is removed, there
may come a time when the first ring is full and sender_body() will move
to the next ring which was never initialized. As a result it will send
all zero packets. (This was discovered when the receiving NIC reported
rx errors.)

Before any transmissions, step through every tx ring and set
NS_BUF_CHANGED on every slot. That will force send_packets() to
initialize the slot when first used. Since it only copies when
necessary, it performs better than always setting OPT_COPY. With this
change, there is no reason for the "drop copy" code.

Submitted by:	Brian Poole <brian90013@gmail.com>
MFC after:	7 days

(cherry picked from commit 506336f2cd1fa0a3ba94bc247d7fad1a71d43ac2)

1 files changed, 14 insertions, 5 deletions

diff --git a/tools/tools/netmap/pkt-gen.c b/tools/tools/netmap/pkt-gen.c
index b06fef05579d..296208018fd4 100644
--- a/tools/tools/netmap/pkt-gen.c
+++ b/tools/tools/netmap/pkt-gen.c
@@ -1604,7 +1604,7 @@ sender_body(void *data)
 	uint64_t n = targ->g->npackets / targ->g->nthreads;
 	uint64_t sent = 0;
 	uint64_t event = 0;
-	int options = targ->g->options | OPT_COPY;
+	int options = targ->g->options;
 	struct timespec nexttime = { 0, 0}; // XXX silence compiler
 	int rate_limit = targ->g->tx_rate;
 	struct pkt *pkt = &targ->pkt;
@@ -1678,6 +1678,19 @@ sender_body(void *data)
 			targ->frags++;
 	}
 	D("frags %u frag_size %u", targ->frags, targ->frag_size);
+
+	/* mark all slots of all rings as changed so initial copy will be done */
+	for (i = targ->nmd->first_tx_ring; i <= targ->nmd->last_tx_ring; i++) {
+		uint32_t j;
+		struct netmap_slot *slot;
+
+		txring = NETMAP_TXRING(nifp, i);
+		for (j = 0; j < txring->num_slots; j++) {
+			slot = &txring->slot[j];
+			slot->flags = NS_BUF_CHANGED;
+		}
+	}
+
 	while (!targ->cancel && (n == 0 || sent < n)) {
 		int rv;
 
@@ -1714,10 +1727,6 @@ sender_body(void *data)
 		/*
 		 * scan our queues and send on those with room
 		 */
-		if (options & OPT_COPY && sent > 100000 && !(targ->g->options & OPT_COPY) ) {
-			D("drop copy");
-			options &= ~OPT_COPY;
-		}
 		for (i = targ->nmd->first_tx_ring; i <= targ->nmd->last_tx_ring; i++) {
 			int m;
 			uint64_t limit = rate_limit ?  tosend : targ->g->burst;