Adaptive Optics rely on a closed loop system featuring challenging real-time constraints. In this context, a response time of under few 100 µs is typically targeted. To achieve this extremely low latency, our team at LESIA developed a GPU-based RTC solution relying on the COSMIC framework. In order to receive frames sent by the WFS camera with very low latency, a custom FPGA board was initially developed. In an effort to adopt standard solutions, the same kind of performance could be achieved using advanced features on high end COTS network controllers (NIC).

In this talk, we will present a new solution based on a COTS NIC and the DPDK gpudev library. This technology enables DMA from NIC to GPU, and makes it possible to reach latencies as low as 4.2 +/- 0.5 µs, a very small portion of the typical time budget for a 10 Gb/s link. We start this presentation by an overview of the MICADO RTC, as well as an introduction of other data acquisition strategies. We continue by diving into the details of our solution and how it was adopted as the baseline solution for this instrument. Finally, we open on the implications of this work, and the impact it could have on other RTC such as on VLT-MAVIS leveraging multiple WFS concurrently, as well as in other domains.

Julien Plante, Observatoire de Paris