Doc tests slow to run

[overlookmotel]

Checklist

• I've looked through the issues and pull requests for similar reports

Describe your issue

On latest Rust (1.90.0) doc tests do run successfully under cross (see #225). However, they're slow.

From our CI logs running cross test --workspace --all-features --target s390x-unknown-linux-gnu:

all doctests ran in 52.48s; merged doctests compilation took 0.84s

https://github.com/oxc-project/oxc/actions/runs/17892348345/job/50874447470#step:5:2553

Without cross-compilation, these doctests run in about ~8s.

Here's the Github Actions workflow using cross: https://github.com/oxc-project/oxc/blob/01859848b19aeb68d55f03418a0e3c08fc37b05a/.github/workflows/ci.yml#L113-L127

I also noticed this in the logs:

WARNING: No rustdoc doctest environment variable provided so doctests will be run in the same process

I'm not sure what this means! But is it possible that what's happening is the old behavior of compiling each doctest as an individual executable? (rather than newer behavior of compiling all doc tests into a single file rust-lang/rust#126245)

What target(s) are you cross-compiling for?

s390x-unknown-linux-gnu

Which operating system is the host (e.g computer cross is on) running?

• macOS
• Windows
• Linux / BSD
• other OS (specify in description)

What architecture is the host?

• x86_64 / AMD64
• arm32
• arm64 (including Mac M1)

What container engine is cross using?

• docker
• podman
• other container engine (specify in description)

cross version

0.2.5

Example

No response

Additional information / notes

No response

[Emilgardis]

How long did it take on 1.89? I remember seeing something about test runners changing how they do stuff, but I havent followed this release closely.

Emulation will add some runtime, so thats expected, im more interested if theres a regression