If you want to count things in data plane nodes, use a per-node counter and the
“show error” debug CLI to inspect it.
To count every packet fed to the node dispatch function, you can bump a node
counter once per frame:
vlib_node_increment_counter (vm, myplugin_node.index,
MYPLUGIN_ERROR_WHATEVER, frame->n_vectors);
A single printf call costs roughly the same number of clock cycles as
processing O(10) packets from start to finish. It’s really expensive.
Dave
From: vpp-dev@lists.fd.io <vpp-dev@lists.fd.io> On Behalf Of Nguy?n Th? Hi?u
Sent: Wednesday, May 6, 2020 5:26 AM
To: vpp-dev@lists.fd.io
Subject: [vpp-dev] Why VPP performance down very much when I use print()
function.
Hi VPP team.
I create a simple VPP node name "swap_mac". "swap_mac" node just swap between
source and destination MAC address and send packet back.
Then, I use Pktgen tool to send packet to VPP. In VPP, the packet will go to
swap_mac->interface-output node and finally send back Pktgen tool.
I found out with this test model, VPP throughput can go up 7Gbps in my lab. But
VPP throughput just is 300Mbps when I add a counter variable to count number of
received packet and a printf() to print value of counter in "swap_mac" node
function.
My code:
counter ++
if((counter % 600.000.000) == 0)
{
printf("Receive packets: %ld", counter );
}
So, why VPP throughput change from 7Gbps to 300Mbps when I just call printf()
function every 600.000.000 packets?
( I have tried to comment out printf() , VPP throughput go up 7Gb again. )
Please help me to see it. I'm sorry for my bad English.
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