[danceparty]

You can get within a few percentage points, yes

I just tested this with two hosts with 4.14.127 upstream kernel and upstream mlx5 driver, and mellanox connectx-5 card. Using 16 iperf threads

[SUM] 0.0-10.0 sec 85.1 Gbits/sec

That's pretty close with no tuning, and well beyond 10gb/s we mentioned earlier

[GhettoMaestro]

Wrong. You’re like an order of magnitude wrong - rofl there is no fucking way the stock Linux kernel will even do 40Mpps at 64 byte packets. It chokes way before that. This is partly why things like DPDK exist.

[ra1n85]

16 iperf threads...sending at what packet size? Do you understand the notion of line rate? 85Gbps at 1500B is only 7MPPS, which is half of 10Gbps at line rate.

[Dylan16807]

Where are you getting your definitions? I have never seen "line rate" used to refer to packets per second.

[ra1n85]

It implies it. Ethernet at 84B per frame is the smallest you can go, thus the line rate - some examples:

https://events19.linuxfoundation.org/wp-content/uploads/2017...

https://www.redhat.com/en/blog/pushing-limits-kernel-network...

https://kernel-recipes.org/en/2014/ndiv-a-low-overhead-netwo...

[Dylan16807]

"How do you fill a 100GBps pipe with small packets?"

"achieve 10 Gbps line rate at 60B frames"

"reaching line rate on all packet sizes"

Line rate is just bits per second. You have to add in a qualifier about packet size before you're talking about packets per second.

[scurvy]

You're both right. It's an older term from the early 90's when a router's selling point was being able to hit "line rate" with the smallest possible packet size. Example, how many tiny datagrams can you forward to fill that link. Back then, people were still doing lots of routing on general purpose machines and Cisco/Juniper were just starting to get into the high performance game.

These days line-rate just means sending enough traffic to fill the link at whatever rate you want. That's generally good enough for server folk since they just want to get you the cat pics ASAP.

That's not good enough for people running transit networks, since they care more about packets per second performance. Sending huge amounts of data is easy for them; what they really care about is PPS.

Aside, the next generations of router NPU's are trash in terms of PPS performance. I take that back, they're not trash. They're the trash in the dumpsterfire. That's how bad they are. We're fairly screwed there.

My guess is GoDaddy was looking at increased PPS performance either for DNS or maybe building their own DDoS mitigation framework (Arbor gear is pricey).

[ra1n85]

Nope, I'm sorry you're not quite getting it here. Minimum Ethernet frame is 84B on the wire - it's simple enough from there.

[big_chungus]

I've never heard this weird qualification for the definition of "line rate" that it somehow requires minimum packet size, so I looked it up. The first three sources for a quoted big-g search all imply or directly state that it's the same as bandwidth:

https://blog.ipspace.net/2009/03/line-rate-and-bit-rate.html

https://www.reddit.com/r/networking/comments/4tk2to/bandwidt...

https://www.fmad.io/blog-what-is-10g-line-rate.html

Also, for gigabit networks, ethernet packets are padded to at least 512 bytes because of a bigger slot size: https://www.cse.wustl.edu/~jain/cis788-97/ftp/gigabit_ethern...

[joemag]

Just like the sibling, I admit I’ve never heard this definition of line rate...

[bogomipz]

No, PPS and bandwidth are two distinct metrics. Although there can be a linear relationship between them line rate does not always imply a payload equal or close to the interface MTU. You see this with network vendors and some of the higher end gear. Network vendors always give specs for their gear by quoting both metrics. And there is some gear that that is capable of doing line rates even with small packets, example the Cisco ASR 1000:

"For example, because one of the newest Cisco routers, the Cisco ASR 1000 Series Router, is capable of forwarding packets at up to 16 Mp/s with services enabled, it can support the processing of the equivalent of 10 Gb/s of traffic at line rate, with services, even for small packets."[1]

[1] https://tools.cisco.com/security/center/resources/network_pe...

[toast0]

Does line rate imply smallest packets? For CDN style use cases, you want to use the whole pipe, and it's going to be mostly larger packets.

[ra1n85]

Yes.

The point of discussion here is that the Linux kernel struggles to do line rate 10Gbps. This was misinterpreted as "the Linux kernel struggles to do 10Gbps".

[gonzo]

You’re sending 1500 byte MTU (1538 bytes on the wire) or maybe larger (9000 byte MTU) packets.

1538 bytes is 12,304 bits. 10,000,000,000 bits/sec / 12,304 bits/packet is 812,744 packets per second.

Now try it with 64 byte packets, which are 84 bytes on the wire.

14,880,952 packets per second.

And this is 10gbps.