It sounds weird, have you commented "if((counter % 600.000.000) == 0)" ？mod
operation maybe expensive since 600,000,000 is a large number than
MAX_INT.
but it should do so much harm to throughput :-(
--
Best Regard
Joe
------------------ Original ------------------
From: "Nguyễn Thế Hiếu"<hieuntg...@gmail.com>;
Date: Wed, May 6, 2020 09:44 PM
To: "Dave Barach (dbarach)"<dbar...@cisco.com>;
Cc: "vpp-dev@lists.fd.io"<vpp-dev@lists.fd.io>;
Subject: Re: [vpp-dev] Why VPP performance down very much when I use
print() function.
Hi Dave & Joe.Thanks for your both answers. I'm glad to see them.
I will try to use vlib_node_increment_counter() function instead.
But I still wonder. I know printf() can be bottleneck of performance, that's
why I just call printf() every 600.000.000 packets.
Even if thoughput is 7Gbps, 600.000.000 packets mean VPP just call
printf() function 1 time per minute.
So, I think at least VPP throughput should be 7Gbps at start testing point and
just down after 1 minute.
But in my case, the throughput is 300Mbps from start testing point.
I have increased 600.000.000 to 1.200.000.000 and got the same result.
Best regards!
HieuNT
Vào Th 4, 6 thg 5, 2020 vào lúc 19:08 Dave Barach (dbarach)
<dbar...@cisco.com> đã viết:
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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