LUPINE: GPU-over-IP

LUPINE is a GPU over IP bridge allowing GPUs on remote machines to be attached to CPU-only machines.

Quick Start

Use the published GHCR images. The examples below pin CUDA 13.3.1 on Ubuntu 24.04; other published tags use the same cuda-<cuda-version>-ubuntu<ubuntu-version> format.

Run the server on the GPU machine:

docker run --rm --gpus all -p 14833:14833 \
  ghcr.io/lupinemachines/lupine-server:cuda-13.3.1-ubuntu24.04

Run the client pointing at that server:

docker run --rm -it \
  -e LUPINE_SERVER=<server>:14833 \
  ghcr.io/lupinemachines/lupine-client:cuda-13.3.1-ubuntu24.04 \
  nvidia-smi

Example output from a real run against a remote RTX 4090:

Mon May 18 15:40:46 2026
+---------------------------------------------------------------------------------------+
| NVIDIA-SMI 535.288.01             Driver Version: 590.48.01    CUDA Version: 13.1     |
|-----------------------------------------+----------------------+----------------------+
| GPU  Name                 Persistence-M | Bus-Id        Disp.A | Volatile Uncorr. ECC |
| Fan  Temp   Perf          Pwr:Usage/Cap |         Memory-Usage | GPU-Util  Compute M. |
|                                         |                      |               MIG M. |
|=========================================+======================+======================|
|   0  NVIDIA GeForce RTX 4090        On  | 00000000:01:00.0  On |                  Off |
| 30%   52C    P8              22W / 450W |      8MiB / 24564MiB |      0%      Default |
|                                         |                      |                  N/A |
+-----------------------------------------+----------------------+----------------------+

+---------------------------------------------------------------------------------------+
| Processes:                                                                            |
|  GPU   GI   CI        PID   Type   Process name                            GPU Memory |
|        ID   ID                                                             Usage      |
|=======================================================================================|
|  No running processes found                                                           |
+---------------------------------------------------------------------------------------+

Inside the client container, LD_LIBRARY_PATH=/opt/lupine/lib is already set, so CUDA driver users pick up the LUPINE libcuda.so.1 shim and NVML users such as nvidia-smi pick up the LUPINE libnvidia-ml.so.1 shim automatically.

Prometheus Metrics

Linux servers built with CUDA and NVML expose Prometheus metrics on the RPC port without monitoring-specific configuration:

curl http://<server>:14833/metrics

The endpoint reports host GPU memory capacity, memory use and utilization, plus memory and utilization for each connected client process. It also exports the mapping between client identity, the Lupine connection child, and the host PID reported by NVML. Values are collected when /metrics is requested, so the server does no background NVML polling.

Client compatibility

Each production server executable embeds the matching Linux, macOS, and Windows client objects for amd64 and arm64; there is no client-bundle directory to deploy beside it. A bundle carries libcuda.so.1 / libcuda.dylib / nvcuda.dll, NVML, and on Linux the NCCL and nvSHMEM shims, which cannot work through the driver by itself. Programs run their own CUDA runtime and libraries against it, so only driver calls cross the wire. Python clients fetch the current object from /.well-known/lupine/client/v1/<os>/<arch>, verify its strong ETag, content digest, manifest, and file hashes, and cache it locally. The selected ETag is also asserted when the RPC connection opens, closing the race between discovery and a server upgrade. LUPINE_LIBDIR remains an explicit local override for development.

Linux client objects target the manylinux_2_28 ABI (glibc 2.28) and statically include their private C++, HTTP/2, and TLS dependencies. They therefore work on newer glibc distributions, including Ubuntu 22.04, without requiring host copies of libstdc++, nghttp2, or OpenSSL. Linux clients require glibc 2.28 or newer; CentOS/RHEL 7 and Ubuntu 18.04 are no longer supported.

Graceful Server Checkpoints

On Linux, SIGTERM stops the server from accepting connections, asks every connection child to finish its in-flight CUDA calls, and waits for those children to exit. This graceful drain happens in the open-source server with no extra runtime dependency.

Each connection child looks for liblupinecr.so.0, then liblupinecr.so, and uses the versioned provider ABI in checkpoint_provider.h. A missing or incompatible provider is a no-op; the server still drains and exits normally. The provider is loaded before the child's first CUDA call so it can observe RM/UVM activity needed to discover allocations.

Set LUPINE_SESSION in the client to attach a stable connection identifier. The optional provider receives that identifier to restore the connection before its first CUDA RPC and checkpoint it after shutdown has drained. For an unkeyed connection, restore is skipped and checkpoint receives a null identifier. Providers own storage configuration, file layout, and any fallback policy for unkeyed connections; Lupine does not select a checkpoint directory.

LUPINE_CHECKPOINT_LIBRARY can override the provider library path for a private deployment.

Connection Stability

Each client/server connection is a single long-lived TCP stream. Long-running workloads sit idle for long stretches (between training steps, during host-side data loading, inside long kernels), and stateful middleboxes — cloud load balancers, NAT gateways, conntrack tables, firewalls — silently reap idle flows far sooner than the kernel's default 2-hour keepalive. The next RPC then fails fatally. Lupine keeps these connections alive and resilient without retrying RPCs (which would break CUDA semantics):

RPC request and response bodies require content-encoding: zstd. Compression is applied transparently at level -1, using one streaming Zstd frame per HTTP/2 body and a 512 KiB history window. RPC boundaries flush the stream without resetting its history. No compression setting is needed. Clients and servers must both support Zstd; older LZ4-only peers are rejected rather than falling back to another encoding. Upgrade the client and server together.

• TCP keepalive is enabled on every connection (client and server) with a 60s idle interval, 15s between probes, and 3 unanswered probes before giving up. Probes are sent only while idle, so active transfers pay no latency cost, and a dead peer is detected in ~105s instead of hanging on the TCP retransmit timer.
• Connect retry rides out a server that is not reachable yet (e.g. still provisioning): a connection is attempted a few times with exponential backoff, and each attempt is bounded by a deadline so a packet-filtered port is detected quickly rather than blocking for the full SYN-retransmit window.

Socket buffer sizes are left to the OS, which auto-tunes on modern kernels.

Trace Logging

Set LUPINE_TRACE on the client, server, or both to enable trace logging. LUPINE_TRACE=0 or an unset value disables tracing. LUPINE_TRACE=1 writes trace output to stdout, LUPINE_TRACE=2 writes it to stderr, and any other non-empty value is treated as a file path opened in append mode.

# trace to stdout
LUPINE_TRACE=1 ./your_cuda_program

# trace to stderr
LUPINE_TRACE=2 ./server

# trace to a file
LUPINE_TRACE=/tmp/lupine.trace ./your_cuda_program

The same LUPINE_TRACE variable controls both client and server tracing; LUPINE_SERVER_TRACE is no longer used.

Device printf Forwarding

LUPINE inspects uploaded PTX and cubin symbol data for vprintf, the CUDA device printf implementation. Until an image that may use device stdout is loaded, synchronization avoids stdout redirection and its process-global lock, allowing independent RPC lanes to synchronize concurrently. Fully opaque compressed fatbins are treated conservatively as potentially using device stdout.

After a device-output-capable image is loaded, context, stream, and event synchronization captures server fd 1 and forwards the bounded CUDA printf buffer to the client's stdout. Capture remains process-global so output from concurrent synchronization lanes is not misattributed.

Multi-GPU Across Multiple Servers

The client accepts a comma-separated LUPINE_SERVER list. Devices are exposed as one local ordinal list in server order: all GPUs from the first server, then all GPUs from the next server, and so on.

Run a server on each GPU machine:

# on gpu-host-a
docker run --rm --gpus all -p 14833:14833 \
  ghcr.io/lupinemachines/lupine-server:cuda-13.3.1-ubuntu24.04

# on gpu-host-b
docker run --rm --gpus all -p 14833:14833 \
  ghcr.io/lupinemachines/lupine-server:cuda-13.3.1-ubuntu24.04

Point the client at both servers:

docker run --rm --network host \
  -e LUPINE_SERVER=gpu-host-a:14833,gpu-host-b:14833 \
  ghcr.io/lupinemachines/lupine-client:cuda-13.3.1-ubuntu24.04 \
  nvidia-smi -L

Expected output lists both remote GPUs:

GPU 0: NVIDIA GeForce RTX 4090 (UUID: GPU-...)
GPU 1: NVIDIA GeForce RTX 4090 (UUID: GPU-...)

CUDA driver applications use the same LUPINE_SERVER value:

docker run --rm --network host \
  -e LUPINE_SERVER=gpu-host-a:14833,gpu-host-b:14833 \
  ghcr.io/lupinemachines/lupine-client:cuda-13.3.1-ubuntu24.04 \
  ./your_cuda_program

Cross-server device-to-device and peer (cuMemcpyDtoD / cuMemcpyPeer) copies are supported: when the source and destination live on different servers, the client transparently stages the data through itself (device->host on one server, then host->device on the other). Direct server-to-server transfers that avoid that client hop, cross-server peer-access enablement, and cuMemcpy3DPeer are not implemented yet. Same-server operations route by handle ownership.

Prefix an endpoint with https:// when the Lupine server is behind a TLS-terminating proxy. Both CUDA applications and NVML tools such as nvidia-smi use the scheme and verify the proxy certificate against the system trust store. HTTPS defaults to port 443; plain and http:// endpoints default to port 14833.

For a specific CUDA version:

docker pull ghcr.io/lupinemachines/lupine-client:cuda-12.4.1-ubuntu22.04
docker pull ghcr.io/lupinemachines/lupine-server:cuda-12.4.1-ubuntu22.04

Client images contain the CUDA driver, NCCL, nvSHMEM, NVML, and HIP shims, their runtime dependencies, and nvidia-smi. Programs bring their own CUDA runtime and libraries. They are based on Ubuntu and contain neither the CUDA nor ROCm SDK. The -slim tags remain available as compatibility aliases with the same SDK-free contents, for example ghcr.io/lupinemachines/lupine-client:cuda-13.3.1-ubuntu24.04-slim.

The server image is also based on Ubuntu. It installs the CUDA compatibility runtime and, on amd64, the ROCm HIP runtime so one image can serve either NVIDIA or AMD GPUs; the older separate HIP server Dockerfile is no longer needed.

Slow Start for the Skeptics

This path derives a small PyTorch client image from the published LUPINE client image and runs the microgpt_train test against a remote GPU. It is intentionally explicit so it is easy to see which side is the CPU-only client and which side owns the GPU.

Create a PyTorch client Dockerfile in the repo root:

# Dockerfile.pytorch-lupine
FROM ghcr.io/lupinemachines/lupine-client:cuda-13.3.1-ubuntu24.04

ARG DEBIAN_FRONTEND=noninteractive

RUN apt-get update && apt-get install -y --no-install-recommends \
    python3 \
    python3-pip \
    && rm -rf /var/lib/apt/lists/*

RUN pip3 install --break-system-packages \
    --index-url https://download.pytorch.org/whl/cu132 \
    torch

COPY test/pytorch_lupine_tests.py /opt/lupine/test/pytorch_lupine_tests.py

ENV LD_LIBRARY_PATH=/opt/lupine/lib:${LD_LIBRARY_PATH}

CMD ["python3", "/opt/lupine/test/pytorch_lupine_tests.py", "microgpt_train"]

Build it:

docker build -f Dockerfile.pytorch-lupine -t lupine-pytorch:cuda-13.3 .

Run the server on the GPU machine:

docker run --rm --gpus all -p 14833:14833 \
  ghcr.io/lupinemachines/lupine-server:cuda-13.3.1-ubuntu24.04

Run the PyTorch client from the CPU-only machine:

docker run --rm \
  -e LUPINE_SERVER=<server>:14833 \
  lupine-pytorch:cuda-13.3

Expected success looks like:

microgpt first_loss=... last_loss=...
microgpt_train: PASS

Local development

Building the binaries requires running codegen first. The repository provides a containerized runner so local development and CI use the same CUDA and HIP headers, Python, parser, and formatter versions. Docker is the only host dependency.

Run codegen

./codegen/run.sh

Ensure there are no errors in the output of the codegen.

Run cmake

cmake -S . -B build
cmake --build build

CMake builds the CUDA driver shim at build/libcuda.so.1, the NCCL shim at build/libnccl.so.2 on Linux (when NCCL 2.14.3 or newer headers are found beside the toolkit's or through -DLUPINE_NCCL_INCLUDE_DIR=<dir>), the nvSHMEM shim at build/libnvshmem_host.so.3 on Linux (when nvSHMEM 3 headers carrying nvshmem_host.h are found beside the toolkit's or through -DLUPINE_NVSHMEM_INCLUDE_DIR=<dir>), the NVML shim at build/libnvidia-ml.so.1, the HIP shim at build/libamdhip64.so.1, and the server at build/lupine_driver_server. A program runs against NVIDIA's own CUDA runtime and libraries on the client; the driver shim forwards the cu* calls they make, and the NCCL shim forwards nccl* calls on the driver shim's connections, so the two must come from the same build. The server loads the machine's libnccl.so.2 by name.

nvSHMEM is the exception: it forwards nothing at all. Its PEs hold a partitioned global address space over the GPUs of a job, reading and writing each other's symmetric heap from inside kernels, and a client is not one of them. The process that owns a GPU here is the server, which serves many clients at once, while nvSHMEM keeps its PE identity, its symmetric heap and its teams in process-global state with no handle to tell one job from another; its heap sits outside the identity VA arena a client reserves; and its device half never reaches a host shim. So the shim loads, answers the version and status queries truthfully, and refuses everything else - nvshmemid_hostlib_init_attr with NVSHMEMX_ERROR_NOT_SUPPORTED, the allocators and peer pointers with null, the collectives with an error - rather than return a value it cannot mean. That is enough for PyTorch, whose libtorch_cuda.so reaches libnvshmem_host.so.3 through libtorch_nvshmem.so in its NEEDED and never calls it unless a program asks for symmetric memory.

A communicator whose ranks sit behind different servers needs those servers to reach each other: NCCL's bootstrap and transport run between the server processes, so settings such as NCCL_SOCKET_IFNAME belong in each server's environment. Drive such ranks from a thread each, as separate processes would; a group reaching two servers from one thread returns ncclInvalidUsage.

Redistributable server builds pass LUPINE_CLIENT_BUNDLE_INPUT with staged native client directories, one lupine-client-<tag> per platform holding the driver and NVML shims and, on Linux, the NCCL and nvSHMEM shims. CMake deterministically assembles all six platform routes from those files alone and links them into lupine_driver_server. The Docker server target requires that generated registry, so a server image cannot be produced without the clients.

The Lupine server must be running before initiating client commands.

./local.sh server

If successful, the server will start:

Server listening on port 14833...

Running the client

For local development, preload the built libcuda.so.1 before executing CUDA commands. The published client image sets LD_LIBRARY_PATH for you instead.

Once the server above is running:

# update to your desired IP/port
export LUPINE_SERVER=<server>:14833

LD_PRELOAD=./build/libcuda.so.1 python3 -c "import torch; print(torch.cuda.is_available())"

# or

LD_PRELOAD=./build/libcuda.so.1 nvidia-smi

You can also use the local shell script to run your commands.

./local.sh run

The opt-in HIP / ROCm test runners build and run upstream hip-tests, rocm-examples, and rocBLAS/hipBLAS clients locally or against an SSH server. They include native baseline runs and a separate CTest project; AMD hardware tests are not enabled in CI.

Questions

1. What does LUPINE stand for? Nothing, it just looks cool in all caps.
2. Does this support authentication? TLS? Indirectly, yes. It's a plain HTTP/2 server, so you can front it with whatever TLS/auth server you want.
3. Was this repo AI-generated? A chunk of it, yes. I mean, would you want to hand write hundreds of tedious API stubs? No? Me neither.
4. Doesn't this incur a lot of latency? Surprisingly, no! You will see device transfers get slower because this is basically bottlenecking a PCIe link over the network, but there is very little overhead besides that. For things like model training and inference, once the model is on the GPU very little data transfer happens to the host. As a result, it might be faster than you expect.
5. Can I do remote video encoding/decoding? This is probably one use case we wouldn't recommend because that's a lot heavier on the PCIe link. It works in theory though, so if you do have access to a 1 Tbps link it might work for you.

Prior Art

This project is inspired by some existing proprietary solutions:

• https://www.thundercompute.com/
• https://www.juicelabs.co/
• https://en.wikipedia.org/wiki/RCUDA

Optional client id

client_id on the monitoring metrics is the client process id. Set LUPINE_WORKLOAD_ID to use that value instead, for example job-123:worker-0. Lupine does not interpret it. Processes that report the same value, from the same address and hostname and with the same process name, share one series for a device. client_pid on lupine_server_connection_info stays the process id either way. The value is attribution metadata, not an authentication credential.

The identifier must be valid UTF-8 and at most 256 bytes. Empty means unset; invalid values are ignored without truncation or disrupting GPU calls. Clients read it when establishing each connection, including reconnects. The existing metadata version is unchanged: the value is an optional trailing extension. Older servers ignore it; newer servers treat metadata from older clients as unset and keep the process id.

lupine_server_connection_info, lupine_client_device_memory_used_bytes and lupine_client_device_utilization_percent carry this client_id. Connections from the same client process that report different values keep the process id. Disconnecting removes the value with its connection registry entry.