几行代码修改引发VPP性能严重下降？

#dpdk 响应的版本及参数
VPP show dpdk version:
DPDK Version:             DPDK 22.07.0
DPDK EAL init args:       --in-memory --no-telemetry --file-prefix vpp -a 0000:4b:00.0,mprq_en=1,rxqs_min_mprq=1,mprq_log_stride_num=9,
txq_inline_mpw=128,rxq_pkt_pad_en=1 
-a 0000:4b:00.1,mprq_en=1,rxqs_min_mprq=1,mprq_log_stride_num=9,
txq_inline_mpw=128,rxq_pkt_pad_en=1 
#l2 
 set interface l2 xconnect HundredGigabitEthernet4b/0/0 HundredGigabitEthernet4b/0/1
 set interface l2 xconnect HundredGigabitEthernet4b/0/1 HundredGigabitEthernet4b/0/0

# l3 routing
 set interface ip address HundredGigabitEthernet4b/0/0 10.10.1.1/24
 set interface ip address HundredGigabitEthernet4b/0/1 10.10.2.1/24
 ip route add 16.0.0.0/8 via 10.10.1.2
 ip route add 48.0.0.0/8 via 10.10.2.2 

#在/etc/vpp/startup.conf文件中dpdk 选项中增加下述配置。
devargs mprq_en=1,rxqs_min_mprq=1,mprq_log_stride_num=9,txq_inline_mpw=128,
rxq_pkt_pad_en=1,dv_flow_en=0

From a9fe20f4b8f7a9bd65cc8ee1b6a0204af7fc3627 Mon Sep 17 00:00:00 2001
From: Fan Zhang <roy.fan.zhang@intel.com>
Date: Thu, 10 Mar 2022 14:49:19 +0000
Subject: [PATCH] dpdk: improve rx burst count per loop

Type: improvement

This patch improves the per dpdk-input loop number of packets
received from the port. The change mimics how packets rx happened
before VPP 22.02/DPDK 21.11: instead of trying to rx huge number
of packets (256) in one go, rx more times with up to 32 packets
max each time.

Signed-off-by: Fan Zhang <roy.fan.zhang@intel.com>
Change-Id: I804dce6d9121ab21b02e53dd0328dc52ac49d80f
---

diff --git a/src/plugins/dpdk/device/node.c b/src/plugins/dpdk/device/node.c
index 0450c42..b460032 100644
--- a/src/plugins/dpdk/device/node.c
+++ b/src/plugins/dpdk/device/node.c
@@ -365,12 +365,13 @@
   /* get up to DPDK_RX_BURST_SZ buffers from PMD */
   while (n_rx_packets < DPDK_RX_BURST_SZ)
     {
-      n = rte_eth_rx_burst (xd->port_id, queue_id,
-                ptd->mbufs + n_rx_packets,
-                DPDK_RX_BURST_SZ - n_rx_packets);
+      u32 n_to_rx = clib_min (DPDK_RX_BURST_SZ - n_rx_packets, 32);
+
+      n = rte_eth_rx_burst (xd->port_id, queue_id, ptd->mbufs + n_rx_packets,
+                n_to_rx);
       n_rx_packets += n;

-      if (n < 32)
+      if (n < n_to_rx)
     break;
     }