What does Bun's cgroup-aware AvailableParallelism mean for Docker?

It ensures Bun apps in Docker containers (--cpus=N) detect exactly N cores, not the host total — preventing oversized thread pools and crashes.

Does Bun now outperform Node in Linux containers?

Yes, with accurate hardwareConcurrency + Bun's baseline speed, expect better resource efficiency and lower latency in k8s/Docker setups.

How to test Bun's new CPU core detection?

`docker run --cpus=2 bun:edge node -e "console.log(os.hardwareConcurrency())"` — should log 2, not host cores.

⚙️ DevOps & Platform Eng

Bun's Linux Containers Finally Report Real CPU Limits

Bun just plugged a massive blind spot in container CPU reporting. Your Node-like apps in Docker now see the actual limits, not the host's full arsenal.

DevTools Feed Apr 03, 2026 3 min read 10 views

⚡ Key Takeaways

Bun now respects Linux cgroup cpu.max for accurate hardwareConcurrency in containers. 𝕏
Fixes oversubscribed threads in Docker/k8s, boosting efficiency. 𝕏
Unique edge: Echoes 2000s VM CPU billing scandals, pushing runtime maturity. 𝕏

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#bun #cgroups #containers #hardwareconcurrency #linux

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