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examples/vhost: fix retry logic on Rx path

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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: be800696c2 ("examples/vhost: use burst enqueue and dequeue from lib")
Cc: stable@dpdk.org

Signed-off-by: Yuan Wang <yuanx.wang@intel.com>
Reviewed-by: Chenbo Xia <chenbo.xia@intel.com>
Tested-by: Wei Ling <weix.ling@intel.com>
This commit is contained in:
Yuan Wang 2022-06-22 17:25:55 +08:00 committed by Maxime Coquelin
parent b90574b10e
commit 1907ce4bae
1 changed files with 11 additions and 17 deletions
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28
examples/vhost/main.c
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@ -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);