patches for DPDK stable branches
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From: Yuan Wang <yuanx.wang@intel.com>
To: maxime.coquelin@redhat.com, chenbo.xia@intel.com, dev@dpdk.org
Cc: jiayu.hu@intel.com, xingguang.he@intel.com,
	cheng1.jiang@intel.com, Yuan Wang <yuanx.wang@intel.com>,
	stable@dpdk.org, Wei Ling <weix.ling@intel.com>
Subject: [PATCH v4] examples/vhost: fix retry logic on eth rx path
Date: Wed, 22 Jun 2022 17:25:55 +0800	[thread overview]
Message-ID: <20220622092555.1149810-1-yuanx.wang@intel.com> (raw)
In-Reply-To: <20220518162505.1691401-1-yuanx.wang@intel.com>

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: stable@dpdk.org

Signed-off-by: Yuan Wang <yuanx.wang@intel.com>
Tested-by: Wei Ling <weix.ling@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


  parent reply	other threads:[~2022-06-22  9:27 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-05-18 16:25 [PATCH] examples/vhost: Fix retry logic on Rx Yuan Wang
2022-05-26  9:30 ` Ling, WeiX
2022-06-17  7:01 ` [PATCH v2] examples/vhost: fix retry logic on eth rx path Yuan Wang
2022-06-20  3:20   ` Xia, Chenbo
2022-06-20  7:36     ` David Marchand
2022-06-20  7:49       ` Xia, Chenbo
2022-06-20  8:59         ` Hu, Jiayu
2022-06-20  9:09           ` Xia, Chenbo
2022-06-20  9:19             ` Wang, YuanX
2022-06-20  9:33               ` Xia, Chenbo
2022-06-20  9:42             ` Hu, Jiayu
2022-06-21 13:34   ` Xia, Chenbo
2022-06-22  2:26     ` Wang, YuanX
2022-06-22  6:27 ` [PATCH v3] " Yuan Wang
2022-06-22  7:23   ` Maxime Coquelin
2022-06-22  8:50     ` Wang, YuanX
2022-06-22  9:25 ` Yuan Wang [this message]
2022-06-23  2:57   ` [PATCH v4] " Xia, Chenbo
2022-06-23  7:20   ` Ling, WeiX
2022-07-01 13:57   ` Maxime Coquelin

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