[PATCH 21.11] examples/vhost: fix retry logic on Rx path
Yuan Wang
yuanx.wang at intel.com
Fri Jul 8 19:14:35 CEST 2022
[ upstream commit 1907ce4baec392a750fbeba5e946920b2f00ae73 ]
drain_eth_rx() uses rte_vhost_avail_entries() to calculate
the available entries to determine if a retry is required.
However, this function only works with split rings, and
calculating packed rings will return the wrong value and cause
unnecessary retries resulting in a significant performance penalty.
This patch fix that by using the difference between tx/rx burst
as the retry condition.
Fixes: be800696c26e ("examples/vhost: use burst enqueue and dequeue from lib")
Signed-off-by: Yuan Wang <yuanx.wang at intel.com>
Reviewed-by: Chenbo Xia <chenbo.xia at intel.com>
---
examples/vhost/main.c | 79 ++++++++++++++++++-------------------------
1 file changed, 33 insertions(+), 46 deletions(-)
diff --git a/examples/vhost/main.c b/examples/vhost/main.c
index 84844da68f..f9e932061f 100644
--- a/examples/vhost/main.c
+++ b/examples/vhost/main.c
@@ -900,31 +900,43 @@ sync_virtio_xmit(struct vhost_dev *dst_vdev, struct vhost_dev *src_vdev,
}
}
-static __rte_always_inline void
-drain_vhost(struct vhost_dev *vdev)
+static __rte_always_inline uint16_t
+enqueue_pkts(struct vhost_dev *vdev, struct rte_mbuf **pkts, uint16_t rx_count)
{
- uint16_t ret;
- uint32_t buff_idx = rte_lcore_id() * MAX_VHOST_DEVICE + vdev->vid;
- uint16_t nr_xmit = vhost_txbuff[buff_idx]->len;
- struct rte_mbuf **m = vhost_txbuff[buff_idx]->m_table;
+ uint16_t enqueue_count;
if (builtin_net_driver) {
- ret = vs_enqueue_pkts(vdev, VIRTIO_RXQ, m, nr_xmit);
+ enqueue_count = vs_enqueue_pkts(vdev, VIRTIO_RXQ, pkts, rx_count);
} else if (async_vhost_driver) {
uint16_t enqueue_fail = 0;
complete_async_pkts(vdev);
- ret = rte_vhost_submit_enqueue_burst(vdev->vid, VIRTIO_RXQ, m, nr_xmit);
- __atomic_add_fetch(&vdev->pkts_inflight, ret, __ATOMIC_SEQ_CST);
+ enqueue_count = rte_vhost_submit_enqueue_burst(vdev->vid,
+ VIRTIO_RXQ, pkts, rx_count);
+ __atomic_add_fetch(&vdev->pkts_inflight, enqueue_count, __ATOMIC_SEQ_CST);
- enqueue_fail = nr_xmit - ret;
+ enqueue_fail = rx_count - enqueue_count;
if (enqueue_fail)
- free_pkts(&m[ret], nr_xmit - ret);
+ free_pkts(&pkts[enqueue_count], enqueue_fail);
+
} else {
- ret = rte_vhost_enqueue_burst(vdev->vid, VIRTIO_RXQ,
- m, nr_xmit);
+ enqueue_count = rte_vhost_enqueue_burst(vdev->vid, VIRTIO_RXQ,
+ pkts, rx_count);
}
+ return enqueue_count;
+}
+
+static __rte_always_inline void
+drain_vhost(struct vhost_dev *vdev)
+{
+ uint16_t ret;
+ uint32_t buff_idx = rte_lcore_id() * MAX_VHOST_DEVICE + vdev->vid;
+ uint16_t nr_xmit = vhost_txbuff[buff_idx]->len;
+ struct rte_mbuf **m = vhost_txbuff[buff_idx]->m_table;
+
+ ret = enqueue_pkts(vdev, m, nr_xmit);
+
if (enable_stats) {
__atomic_add_fetch(&vdev->stats.rx_total_atomic, nr_xmit,
__ATOMIC_SEQ_CST);
@@ -1217,44 +1229,19 @@ drain_eth_rx(struct vhost_dev *vdev)
if (!rx_count)
return;
- /*
- * When "enable_retry" is set, here we wait and retry when there
- * is no enough free slots in the queue to hold @rx_count packets,
- * to diminish packet loss.
- */
- if (enable_retry &&
- unlikely(rx_count > rte_vhost_avail_entries(vdev->vid,
- VIRTIO_RXQ))) {
- uint32_t retry;
+ enqueue_count = enqueue_pkts(vdev, pkts, rx_count);
- for (retry = 0; retry < burst_rx_retry_num; retry++) {
+ /* Retry if necessary */
+ if (enable_retry && unlikely(enqueue_count < rx_count)) {
+ uint32_t retry = 0;
+
+ while (enqueue_count < rx_count && retry++ < burst_rx_retry_num) {
rte_delay_us(burst_rx_delay_time);
- if (rx_count <= rte_vhost_avail_entries(vdev->vid,
- VIRTIO_RXQ))
- break;
+ enqueue_count += enqueue_pkts(vdev, &pkts[enqueue_count],
+ rx_count - enqueue_count);
}
}
- if (builtin_net_driver) {
- enqueue_count = vs_enqueue_pkts(vdev, VIRTIO_RXQ,
- pkts, rx_count);
- } else if (async_vhost_driver) {
- uint16_t enqueue_fail = 0;
-
- complete_async_pkts(vdev);
- enqueue_count = rte_vhost_submit_enqueue_burst(vdev->vid,
- VIRTIO_RXQ, pkts, rx_count);
- __atomic_add_fetch(&vdev->pkts_inflight, enqueue_count, __ATOMIC_SEQ_CST);
-
- enqueue_fail = rx_count - enqueue_count;
- if (enqueue_fail)
- free_pkts(&pkts[enqueue_count], enqueue_fail);
-
- } else {
- enqueue_count = rte_vhost_enqueue_burst(vdev->vid, VIRTIO_RXQ,
- pkts, rx_count);
- }
-
if (enable_stats) {
__atomic_add_fetch(&vdev->stats.rx_total_atomic, rx_count,
__ATOMIC_SEQ_CST);
--
2.25.1
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