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* [dpdk-dev] [PATCH v2] virtio: Fix vring entry number issue
@ 2014-10-11  8:05 Ouyang Changchun
  2014-10-14 15:12 ` [dpdk-dev] [PATCH v3] " Ouyang Changchun
  0 siblings, 1 reply; 8+ messages in thread
From: Ouyang Changchun @ 2014-10-11  8:05 UTC (permalink / raw)
  To: dev

-- V1 change:
  Fix one issue in virtio TX: it needs one more vring descriptor to hold the virtio 
  header when transmitting packets, it is used later to determine whether to free
  more entries from used vring.

  It fixes failing to transmit any packet with 1 segment in the circumstance of only
  1 descriptor in the vring free list.

-- V2 change:
  Refine description, 'vring descriptor' is more accurate than 'vring entry';
  Accordingly update test condition (it needs one more descriptor for virtio header) to 
  put packets to transmit queue.
 
Signed-off-by: Changchun Ouyang <changchun.ouyang@intel.com>
---
 lib/librte_pmd_virtio/virtio_rxtx.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/lib/librte_pmd_virtio/virtio_rxtx.c b/lib/librte_pmd_virtio/virtio_rxtx.c
index 0b10108..c736362 100644
--- a/lib/librte_pmd_virtio/virtio_rxtx.c
+++ b/lib/librte_pmd_virtio/virtio_rxtx.c
@@ -699,7 +699,8 @@ virtio_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts, uint16_t nb_pkts)
 	num = (uint16_t)(likely(nb_used < VIRTIO_MBUF_BURST_SZ) ? nb_used : VIRTIO_MBUF_BURST_SZ);
 
 	while (nb_tx < nb_pkts) {
-		int need = tx_pkts[nb_tx]->pkt.nb_segs - txvq->vq_free_cnt;
+		/* Need one more descriptor for virtio header. */
+		int need = tx_pkts[nb_tx]->pkt.nb_segs - txvq->vq_free_cnt + 1;
 		int deq_cnt = RTE_MIN(need, (int)num);
 
 		num -= (deq_cnt > 0) ? deq_cnt : 0;
@@ -708,7 +709,12 @@ virtio_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts, uint16_t nb_pkts)
 			deq_cnt--;
 		}
 
-		if (tx_pkts[nb_tx]->pkt.nb_segs <= txvq->vq_free_cnt) {
+		need = (int)tx_pkts[nb_tx]->pkt.nb_segs - txvq->vq_free_cnt + 1;
+		/*
+		 * Zero or negative value indicates it has enough free
+		 * decriptors to transmit.
+		 */
+		if (need <= 0) {
 			txm = tx_pkts[nb_tx];
 			/* Enqueue Packet buffers */
 			error = virtqueue_enqueue_xmit(txvq, txm);
-- 
1.8.4.2

^ permalink raw reply	[flat|nested] 8+ messages in thread

end of thread, other threads:[~2014-10-15  6:27 UTC | newest]

Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2014-10-11  8:05 [dpdk-dev] [PATCH v2] virtio: Fix vring entry number issue Ouyang Changchun
2014-10-14 15:12 ` [dpdk-dev] [PATCH v3] " Ouyang Changchun
2014-10-14 15:28   ` Ouyang, Changchun
2014-10-14 16:03   ` [dpdk-dev] [PATCH v4] " Ouyang Changchun
2014-10-14 16:26     ` Xie, Huawei
2014-10-15  3:14       ` Ouyang, Changchun
2014-10-15  3:11     ` [dpdk-dev] [PATCH v5] " Ouyang Changchun
2014-10-15  6:34       ` Thomas Monjalon

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