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")
Cc: sta...@dpdk.org
Signed-off-by: Yuan Wang <yuanx.w...@intel.com>
Tested-by: Wei Ling <weix.l...@intel.com>
---
V4: Fix fiexs tag.
V3: Fix mbuf index.
V2: Rebase to 22.07 rc1.
---
examples/vhost/main.c | 28 +++++++++++-----------------
1 file changed, 11 insertions(+), 17 deletions(-)
diff --git a/examples/vhost/main.c b/examples/vhost/main.c
index e7fee5aa1b..0fa6c096c8 100644
--- a/examples/vhost/main.c
+++ b/examples/vhost/main.c
@@ -634,7 +634,7 @@ us_vhost_usage(const char *prgname)
{
RTE_LOG(INFO, VHOST_CONFIG, "%s [EAL options] -- -p PORTMASK\n"
" --vm2vm [0|1|2]\n"
- " --rx_retry [0|1] --mergeable [0|1] --stats [0-N]\n"
+ " --rx-retry [0|1] --mergeable [0|1] --stats [0-N]\n"
" --socket-file <path>\n"
" --nb-devices ND\n"
" -p PORTMASK: Set mask for ports to be used by
application\n"
@@ -1383,27 +1383,21 @@ 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 = vdev_queue_ops[vdev->vid].enqueue_pkt_burst(vdev,
+ VIRTIO_RXQ, 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 +=
vdev_queue_ops[vdev->vid].enqueue_pkt_burst(vdev,
+ VIRTIO_RXQ,
&pkts[enqueue_count],
+ rx_count -
enqueue_count);
}
}
- enqueue_count = vdev_queue_ops[vdev->vid].enqueue_pkt_burst(vdev,
- VIRTIO_RXQ, pkts, rx_count);
-
if (enable_stats) {
__atomic_add_fetch(&vdev->stats.rx_total_atomic, rx_count,
__ATOMIC_SEQ_CST);
--
2.25.1
