Performance issues when using the Network API used to create a web server

Question

Created 4d

Replies 5

Boosts 0

Participants 2

Hello,

We use the Network API in our macOS ObjectiveC applications to create a small web server. With macOS Sequoia or Tahoe (not with Sonoma), downloading files from another computer using the built-in ethernet port is way too slow.

Steps to reproduce:

Computer A (using macOS Tahoe or Sonoma), run an application using the Network APIs to create a webserver
Make sure that this computer connects to the network using the Ethernet port, there is no issue when using WiFi
On computer B, make an HTTP request to download a 20MB file => it will take about 30 seconds to download => way too slow...

We tested with:

if on computer A you run a web server using the GCD API instead of Network, it takes 0.2 seconds to download the file => no issue
on computer A disable TSO, it improves the results, but that's not a long term solution as it doesn't hold when rebooting

I can provide sample code to demonstrate this if needed.

This is a new issue as it's been a while we use that code, and only noticed it recently, and macOS Sonoma is not impacted.

Thank you for the help you can provide.

Pierre

Boost

Answer 1

chevalierpg OP

3d

Here's a link to download a sample code that will run a server with the Network API and with the GCD API.

Instructions are included, in the "Instructions.txt" file, as you may have guessed. ;-) https://softron-downloads.s3.amazonaws.com/bvcwb546r7ret8hyj9tpm413a57zagf6qdf6h8/DualHTTPServer.zip

Thank you!

Pierre

0

Answer 2

DTS Engineer OP

Apple

1d

Computer A (using macOS Tahoe or Sonoma)

You mean “macOS Tahoe or Sequoia”, right? That is, macOS 26 or macOS 15?

[My experience is that it’s better to stick with version numbers rather than names. In 5 years time, it’s gonna be really hard to remember whether macOS Sequoia came before or after macOS Sonoma.]

On computer B, make an HTTP request to download a 20MB file

Is this using your own HTTP client? Or URLSession? Or curl? Or something else?

Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

0

Answer 3

chevalierpg OP

16h

Hi Quinn,

Thank you for getting back to me.

Yes I do mean macOS 26 or macOS 15. Earlier macOS versions do not show the issue. Note that we only tested with macOS 15.6.1, macOS 26.0.1 and macOS 26.1 beta 3 and 4.

In the sample code and instructions that I provided, we can reproduce it with curl, but we have seen the issue first in our code where we use URLSession.

Let me know if you need additional information.

Pierre

0

Answer 4

DTS Engineer OP

Apple

13h

Thanks for the extra.

Another question:

there is no issue when using WiFi

I’d like to clarify what you mean by “no issue” here. In general, I’d expect Wi-Fi to be slower than Ethernet, but it doesn’t seem like it’d be slow enough to mask this issue. So imagine these scenarios:

Server   | Network API | Speed
------   | ----------- | -----
Dispatch | Ethernet    | A
Dispatch | Wi-Fi       | B
Network  | Ethernet    | C
Network  | Wi-Fi       | D

In both servers I’d expect to see a slight performance loss from Ethernet to Wi-Fi, but it sounds like you’re seeing a much greater performance loss in the Network framework case. That is, the C:D ratio is wildly different than the A:B ratio.

Is that right?

Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

0

Answer 5

chevalierpg OP

11h

Hi Quinn,

Thank you for your quick answer.

You are correct, the issue is that the C:D ratio is wildly different than the A:B ratio.

To be more specific, below are the results we can see to download a 20MB file, depending on your cases above (A, B, C or D).

1. Server on macOS 26.1, or macOS 15.6.1

With TSO enabled:

A: Download time: 0.208543s, Bytes: 20971520, Speed: 100562090 bytes/sec
B: Download time: 0.638284s, Bytes: 20971520, Speed: 32856095 bytes/sec
C: Download time: 23.000043s, Bytes: 20971520, Speed: 911803 bytes/sec
D: Download time: 3.259781s, Bytes: 20971520, Speed: 6433413 bytes/sec

As you can see, with ethernet, a server in GCD takes less than 1 second to download a 20MB file, while with Network, it takes more than 20 seconds.

In Wifi, it's slightly better, but still slower than GCD.

With TSO disabled:

If on the server side, we disable TSO using sudo sysctl -w net.inet.tcp.tso=0

A: Download time: 0.208460s, Bytes: 20971520, Speed: 100602129 bytes/sec
B: Download time: 0.672691s, Bytes: 20971520, Speed: 31175562 bytes/sec
C: Download time: 1.865778s, Bytes: 20971520, Speed: 11240093 bytes/sec
D: Download time: 2.332780s, Bytes: 20971520, Speed: 8989926 bytes/sec

It is much better for case C.

2. Server on macOS 14.7

With TSO enabled:

A: Download time: 0.232860s, Bytes: 20971520, Speed: 90060637 bytes/sec
B: Download time: 0.680401s, Bytes: 20971520, Speed: 30822294 bytes/sec
C: Download time: 6.255250s, Bytes: 20971520, Speed: 3352626 bytes/sec
D: Download time: 7.912810s, Bytes: 20971520, Speed: 2650325 bytes/sec

A server using Network is still slowed than GCD, but it is much better than on macOS 26 and 15.

With TSO disabled:

A: Download time: 0.236461s, Bytes: 20971520, Speed: 88689128 bytes/sec
B: Download time: 0.707016s, Bytes: 20971520, Speed: 29662016 bytes/sec
C: Download time: 6.275888s, Bytes: 20971520, Speed: 3341602 bytes/sec
D: Download time: 6.758729s, Bytes: 20971520, Speed: 3102879 bytes/sec

Difference is marginal, so disabling TSO has no impact on macOS 14.7.

I hope it clears things up. Let me know if you need more info.

Pierre

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