Xcode 16.4 - SPM loads some dependencies slow

[findthebug]

We are using Tart VM in combination with Xcode 16.4 to build apps (triggered via GitLab pipelines).

Since upgrading to Xcode 16.4 last week, we’ve noticed that some Swift package dependencies (random ones) are loaded extremely slowly inside the VM, even though they are small packages. Some downloads take up to 20 minutes.

The same project resolves all dependencies within seconds on the host machine.

Internet inside the VM & Host is confirmed to be fast—e.g., direct downloads and pings are quick—so this doesn't seem to be a raw network issue.

Environment:
VM Image: ghcr.io/cirruslabs/macos-sequoia-xcode:latest
Executor Version: 1.25.1
Tart Version: 2.28.2
Xcode Version: 16.4

Notes:

• Issue started with Xcode 16.4.
• Affects Swift Package Manager (SPM) dependency resolution.
• The issue seems random and doesn’t affect the same packages consistently.
• No problems on host macOS using the same project setup.
• Since some dependencies take then up to 50minutes we run into pipeline timeouts.

Looking for any ideas or known issues related to:

• Networking or I/O in Tart VM
• SPM changes in Xcode 16.4
• VM image performance quirks

Today I updated everything, but the behavior is the same as with the older versions.
Is anyone else experiencing this issue? I'm running out of ideas.

Is there a way to get some logs from the network stack in tart?

[edigaryev]

There's no networking stack in Tart per se, it's all provided by Apple through Virtualization.Framework.

We have a Softnet, though, which may help in certain cases, see #258 (comment).

1. Could you try running tart run with --net-softnet to see if it improves anything?

2. Which other arguments and/or environment variables do you pass to tart run?

3. Which hardware do you run this on? Is it an AWS machine by a chance?

[findthebug]

Hardware:
Apple Mac Mini M1 (16GB Ram)

We do not use any parameter, heres the executor config.

One question regarding your suggested --net-softnet parameter: do i need to install the softnet package for this to work? since our mac mini is inside a datacenter and im not sure i can risk to change networks setting on the mac itself. or is this package not touching hardware network settings?

Or can i just use --net-softnet without softnet? thanks!

[edigaryev]

Sorry, I've missed the part about GitLab Tart Executor.

To enable Softnet, you just need to set TART_EXECUTOR_SOFTNET environment variable to true, see https://github.com/cirruslabs/gitlab-tart-executor?tab=readme-ov-file#supported-environment-variables.

Softnet is pulled automatically as a dependency to cirruslabs/cli/tart.

[findthebug]

The mac mini is a managed device, so i can't modify the permissions to use softnet this way.

[edigaryev]

The mac mini is a managed device, so i can't modify the permissions to use softnet this way.

You can set this environment variable directly in the .gitlab-ci.yml.

[findthebug]

That .yml part is working. I'm talking about the setup of Softnet. The software needs special permissions to execute properly, and I'm not sure I can do this on the Mac Mini since it's a managed device with restricted permissions.

https://github.com/cirruslabs/softnet?tab=readme-ov-file#installing

This is the message from the runner:

will do some test and see if i can get the permission fixed.

[findthebug]

I pulled the same VM to my local mac and did test with same project. I can't reproduce it on local mac, so it needs to be on the mac mini. i was thinking about DNS issues so i cleared DNS cache: sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder, also deleted the /var/db/dhcpd_leases on mac mini.

or maybe it's xCode related since we used an older version of xCode and we never experienced this before.