Add ubuntu 20.04 image for linux-riscv64

[luhenry]

No description provided.

[luhenry]

I've also verified that the resulting image can build rocksdb with:

podman run --rm -it --platform linux/riscv64 -v /path/to/rocksdb:/rocksdb -w /rocksdb -v ~/.m2:/root/.m2 localhost/evolvedbinary/rocksjava:ubuntu20_riscv64-be bash -ex -c "make rocksdbjava"

[adamretter]

@luhenry This looks like a great addition, but we don't have suitable hardware to be able to test this on. Also I see it uses JDK 11, but we require JDK 8 for building RocksJava.

[luhenry]

we don't have suitable hardware to be able to test this on

We could be using QEMU on x86_64 or aarch64 machines to test the functionality. I could get that working if you are interested.

I see it uses JDK 11, but we require JDK 8 for building RocksJava.

JDK 8 is not available on RISC-V, and I don't expect it to be ever. The backport would is just too much work, and RISC-V is a new enough platform that people stuck on JDK 8 are very unlikely to switch to RISC-V. Is there any other concern on using JDK 11 on RISC-V specifically?

[adamretter]

We could be using QEMU on x86_64 or aarch64 machines to test the functionality

We have a bunch of servers running KVM and QEMU, however in the past when we have tried to emulate RISC-V, we were able to get a Ubuntu installed, however we then could not get Docker running on RISC-V as that appeared unsupported, at least at that time under Ubuntu - has that changed now?

JDK 8 is not available on RISC-V, and I don't expect it to be ever

Okay understood.

Is there any other concern on using JDK 11 on RISC-V specifically?

In practice probably not. Just to say that we don't code for it or test with it yet. As RocksDB is a widely used library we aim for a lowest common denominator of both libc (or muslc) library ABI, and JLS version. This allows the widest audience possible to use the binaries of the library without having to compile it themselves.
Ideally we target Java 1.8, but if that isn't supported on RISC-V, then a newer version could be used to produce RISC-V binaries.

[luhenry]

We have a bunch of servers running KVM and QEMU, however in the past when we have tried to emulate RISC-V, we were able to get a Ubuntu installed, however we then could not get Docker running on RISC-V as that appeared unsupported, at least at that time under Ubuntu - has that changed now?

I've been running QEMU on Ubuntu on Github Actions CI on multiple projects. https://github.com/uraimo/run-on-arch-action/ is an example of how to do it on GHA. I'm happy to reproduce something similar on CircleCI.

[adamretter]

@luhenry Okay I now have a Ubuntu 22.04 emulated RISC-V 64 VM running on KVM/QEMU on Ubuntu 22.04 x86_64, and I have managed to install Docker 24.0.5 on there. See - https://blog.adamretter.org.uk/ubuntu-riscv64-guest-on-kvm/

I am surprised by quite how slow the emulation is though!

I will now try and test out your Docker image PR...

[adamretter]

@luhenry I have now tested this and it appears to work well, thank you very much for your PR, and sorry for the delay in being able to test this.

[adamretter]

I have now also pushed the image to Docker Hub - evolvedbinary/rocksjava:ubuntu20_riscv64-be

[luhenry]

I am surprised by quite how slow the emulation is though!

It's not fast indeed :) Usually around 10x slower per-core. It's important to use multithreading/multiprocessing as much as you can just to hide that slowness

[luhenry]

Thank you for merging the PR, I'll submit the follow up changes for rocksdb in the coming days.