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From: Ouyang Changchun <changchun.ouyang@intel.com>
To: dev@dpdk.org
Subject: [dpdk-dev] [PATCH v2] virtio: Fix vring entry number issue
Date: Sat, 11 Oct 2014 16:05:35 +0800
Message-ID: <1413014735-24693-1-git-send-email-changchun.ouyang@intel.com> (raw)

-- 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

             reply	other threads:[~2014-10-11  7:58 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-10-11  8:05 Ouyang Changchun [this message]
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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