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Comment by est | Hacker News Reader

> Prerequisites Install QEMU

So in other words, qemu runs at near-native speeds?

QEMU can use the MacOS virtualization framework layer to run a VM built for the same arch without going through any translation.

From there you can register Rosetta as a runtime and use it to run x86-64 Linux apps on ARM64 if you want. (https://developer.apple.com/documentation/virtualization/run...)

Wait, what? QEMU can pass x86 instructions directly to Rosetta without emulating an entire host OS?

No, QEMU runs an ARM VM. Inside that VM, Rosetta for Linux can be used to run x86 executables, just like on macOS.

so arm macbooks are still problematic for developers who use containers and x86 servers...

it's still surprising to me that they did this as i always got the sense that developer word of mouth helped drive a lot of macbook adoption in the 2000s.

In what way?

I use ARM containers locally to dev and test locally, check in the code and the build server creates an x86 image for deployment to the server.

Worst case you have to build the ARM container yourself locally and tag it with the "remote" name and docker will just use it instead of pulling the remote version.

you have to add support for your infrastructure to support building of everything for two architectures. sometimes problems are architecture dependent. if you have to use x86 containers for some reason, they will be dog slow because you'll be running the kernel under emulation and in userland rosetta won't help.

Not dog slow but slower than they could. My experience is: a Rails test suite takes 75 seconds on my 2014 Intel ZBook laptop with a SATA bus and a SSD. It takes 50 seconds on a M1 MacBook. I'm sure I could have found some expensive Intel laptop as fast as that back in 2014. Docker on the M1 runs with something called Mutagen and we have two different docker-compose.yml, but one Dockerfile.

Rosetta absolutely does help. You register rosetta (which can be mounted into the VM using macOS's virtualization framework) with binfmt_misc and your x86 binaries inside the VM will run through Rosetta.

Rosetta doesn’t help here because the kernel would be ARM, and the parent commenter wants an x86-64 kernel.

X86 userspace on an arm kernel is exactly what Rosetta would be used for.

Sure, but they are talking about an Intel kernel.

Doh! I see now.

My whole team got M1s, so we just use ARM images on AWS. Haven't had any problems.

Aside from the basis of your comment being not really true (as mrunkel commented), every thread about Apple Silicon Macs is full of people praising the performance and battery life. This is more positive word-of-mouth than Apple's had in years.

It does emulate the OS (it’s the point of running stuff in qemu ) but doesn’t translate the instructions

> It does emulate the OS (it’s the point of running stuff in qemu)

The point of running stuff in qemu is to virtualize / emulate the hardware. You still need a “normal” OS inside qemu.

I don't understand why one needs to emulate a virtual machine to run a container. Why do you need a kernel? Why emulate physical devices, interrupts and everything else? Why cannot one run a container as a protected mode application?

Because containers are at their heart a shorthand term for a bunch of Linux kernel features that do not exist on other OSes.

Adding to other answers, not only containers of the docker and LXC/D types are Linux things that need a Linux kernel but often the software inside the container must be deployed and run on a Linux host. Often the build is done on a Linux server in a CI system and not on developers machines but developers do have to run that software too, kind of by definition.

Containers are just fancy Linux chroots. So you need a Linux OS.

It’s difficult to emulate a kernel. You can try and there have been multiple attempts to do so with varying levels of success but most have pitfalls that people eventually run into.

You don't and that's the idea behind gVisor.

Well yeah bc it uses https://developer.apple.com/documentation/virtualization/run...

Yes, on recent MacOS it is mostly just an abstraction on top of the native Virtualization Framework.

Not if you’re running x86 emulation on an ARM host. It’s terribly slow.

EDIT: This is from experience. When I started using a M1 mac, our docker builds on x86 images took up to 5x or 10x longer vs running on an arm64 image. Had slightly faster, but similar results running my own docker host on Lima, or podman, or building without docker inside a UTM host which also uses qemu.

I don’t think that’s true.

https://developer.apple.com/documentation/virtualization/run...

Requires an arm64 kernel. Rosetta in this context essentially replaces usermode QEMU.

No, it's decent performance. Minimum 25% of native, and even more using Rosetta: https://news.ycombinator.com/item?id=32149080

For real world use cases like making cross-platform builds, 1/4 of native speed is pretty far from decent.

It's not abstraction, QEMU uses Hypervisor framework (which is equivalent to KVM). Virtualization framework is Apple own hypervisor (which is equivalent to QEMU).

Well, it can be. You can still emulate additional hardware with QEMU, and QEMU still has other backends (which it will use if you run a x86-64 OS on ARM macs).

Not right now. Can be an order of magnitude slower compared to native. Depends a lot on the program and current task. Also, the QEMU defaults are not optimal.

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