[zbentley]

> Docker for Mac uses QEMU for `--platform`

Only on older setups and on the default config. Updated MacOS (13+) and updated docker provides an option to use Rosetta and the new virtualization system. That, I believe, replaces QEMU for x86 emulation with the Apple emulator.

I've had substantial success with that method; not only does it seem a bit faster, but some containerized apps that very frequently failed to start (e.g. Apache Pulsar) work consistently in that mode. I suspect this difference in experience speaks to bugs in QEMU that trigger in the presence of certain application behavior (in Pulsar's case, something weird happening with the JVM on startup).

QEMU's still an incredible feat of engineering and something I frequently use on Linux, though. It just seems that the Apple emulation on Macs is better (which makes sense, given that it's built by the people who made the semi-proprietary silicon it's emulating from).

[xp84]

Can I ask a question? It seems like your post is combining two separate things. As I understand it and based on earlier comments in the thread:

1. To run a Linux container you need to be running Linux 2. This is why Docker for Max has always run a VM under the covers. It uses qemu. 3. This was true even before Apple Silicon when everything was x86_64 and nothing was emulated

Now you are bringing up Rosetta and x86 emulation. While I understand sometimes it’s necessary to run a container that hasn’t been compiled for aarch64 (or whatever they call Apple) so I can see why the actual cpu emulation capabilities of qemu or Rosetta would be necessary there, this seems to be beside the point.

if you have no Linux system involved because you have no VM, how would that work? What would the base system “under” the container be and what would respond to Linux’s OS-level calls?

[zbentley]

This is the core of my challenges:

> sometimes it’s necessary to run a container that hasn’t been compiled for aarch64

I have several containers in that boat, for which no ARM versions exist at all. Those containers were previously using QEMU to emulate x86 on ARM linux (in Docker's VM on an ARM Mac). That emulation encountered the failures I described, and was slow.

Switching to use Rosetta 2 in Docker solved the problems; the process for enabling it is described here: https://levelup.gitconnected.com/docker-on-apple-silicon-mac...

Something I don't know and am curious about is how Docker-for-Mac is actually using Rosetta 2. Is it running an additional Linux VM containing an x86 Linux OS, and running that VM through a Rosetta-2-enabled hypervisor? Or is Rosetta 2 distributed as a Linux program that is being invoked inside Docker's pre-existing aarch64 Linux VM instead of (or inside of?) QEMU?

Edit: as for your question:

> if you have no Linux system involved because you have no VM, how would that work?

That's not my situation, so I'm not sure.

[sgerenser]

Yes, Rosetta 2 is being used by Docker’s pre-existing aarch64 Linux VM. So it’s only translating userspace x86 code to Arm, then running it on the ARM Linux VM. Syscalls, etc. are still handled by the (aarch64) Linux VM.