Async/Await on the GPU (opens in new tab)

We have been curious about this for rapids cudf. We built the graphistry stack 10 years ago (!) for GPU native end-to-end acceleration - data loading, wrangling, analytics, enrichment, viz, etc, all the way server GPUs to client GPUs - but this has been a huge sticking point. Major constant overheads for smaller workloads that seem avoidable.

Essentially, we solved the problem of writing our stack in a bulk-oriented way that Nvidia kernels can optimize. Think apache arrow, pure vectorized dataframe pipelines, etc. However, cudf is 'eager' with per-step CPU/GPU control plane coordination, even if the data plane lives on the GPU. Polars in theory moves to lazy scheduling that can allow deforesting optimizations for more bulk GPU-side control macro steps, but not really. Nvidia efforts to cut python asyncio costs for multitenant etc flows didn't pan out either. So enabling moving more to the GPU here is super interesting.

Will be watching!

I'm not quite seeing the real benefit of this. Is the idea that warps will now be able to do work-stealing and continuation-stealing when running heterogenous parallel workloads? But that requires keeping the async function's state in GPU-wide shared memory, which is generally a scarce resource.

Really cool experiment (the whole company).

Training pipelines are full of data preparation that are first written on CPU then moving to GPU and always thinking of what to keep on CPU and what to put on GPU, when is it worth to create a tensor, or should it be tiling instead. I guess your company is betting on solving problems like this (and async-await is needed for serving inference requests directly on the GPU for example).

My question is a little bit different: how do you want to handle the SIMD question: should a rust function be running on the warp as a machine with 32 long arrays as data types, or always ,,hope'' for autovectorization to work (especially with Rust's iter library helpers).

What's the performance like? What would the benefits be of converting a streaming multiprocessor programming model to this?

One concern I have is that this async/await approach is not "AOT"-enough like the Triton approach, in the sense that you know how to most efficiently schedule the computations on which warps since you know exactly what operations you'll be performing at compile time.

Here with the async/await approach, it seems like there needs to be manual book-keeping at runtime to know what has finished, what has not, and _then_ consider which warp should we put this new computation in. Do you anticipate that there will be measurable performance difference?

The CPU to GPU dispatch overhead this aims to eliminate is a real bottleneck I've measured: my multi-pass Winograd kernel on MI300X (github.com/Jayluci4/nova-wino-amd) launches 3 HIP kernels + 1 rocBLAS GEMM per forward pass — 17-57% faster than MIOpen at batch=1, but at batch=8+ the dispatch latency between stages completely dominates and a fused single-dispatch kernel wins by 2-4x. On the AMD wavefront question: CDNA3's 64-lane wavefront vs NVIDIA's 32-lane warp changes the async scheduling model — you get 64-element register swaps via __shfl in one cycle (my transforms do full 8x8 matrix multiplies through wave shuffles with zero shared memory), but 64-wide means coarser divergence granularity for heterogeneous coroutine paths. An async execution model that pipelines multi-pass kernels without CPU round-trips would directly close the batch>1 gap for workloads like Winograd convolution, batched flash attention, and MoE expert dispatch. @magic_at_nodai — happy to help test AMD support when the time comes; I have working HIP kernels with wave shuffles and MFMA accumulation that would be a good real-workload stress test for the async dispatch model

Love this.

You mention futures are cooperative and GPUs lack interrupts, but GPU warps already have a hardware scheduler that preempts at the instruction level. ARe you intentionally working above that layer, or do you see a path to a fture executor that hooks into warp scheduling more directly to get preemptive-like behavior?

Very cool to see this and something I have been curious about myself and exploring the space as well. I'd be curious what are some parallels and differentiations between this and NVIDIA's stdexec (outside of it being in Rust and using Future, which is also cooL)

Is this Nvidia-only or does it work on other architectures?

AS I know GPUs execute code pretty fast as long as all threads in a warp go the same execution path. Branching causes performance degradation. But executing exactly the same code for multiple coroutines seems for me to be practically impossible. So, can good performance be reached with such approach at all?

Very interesting. What is the runtime model, based on the "async trilema" https://without.boats/blog/the-scoped-task-trilemma/ ?

I assume tokio-like, i.e. work-stealing?

Warp specialization is an abomination that should be killed and I'm glad this could be an alternative.

I hope they can minimize the bookkeeping costs because I don't see it gain traction in AI if it hurts big kernels performance.

Very cool!

Is the goal with this project (generally, not specifically async) to have an equivalent to e.g. CUDA, but in Rust? Or is there another intended use-case that I'm missing?

Et tu, GPU?

I am, bluntly, sick of Async taking over rust ecosystems. Embedded and web/HTTP have already fallen. I'm optimistic this won't take hold in GPU; well see. Async splits the ecosystem. I see it as the biggest threat to Rust staying a useful tool.

I use rust on the GPU for the following: 3d graphics via WGPU, cuFFT via FFI, custom kernels via Cudarc, and ML via Burn and Candle. Thankfully these are all Async-free.

genius, great idea and follow through, please keep it up, this could improve the ML industry tremendously, maybe some einops inspired interface for this would be good?