whats the status of dma support of quot ethernet over pcie quot in jetpack 4.3

In https://devtalk.nvidia.com/default/topic/1050616/jetson-agx-xavier/the-bandwidth-of-of-virtual-ethernet-over-pcie-between-two-xaviers-is-low/3, vidyas said that “DMA support would be available in next release.”

In https://devtalk.nvidia.com/default/topic/1057581/jetpack-4-2-1-l4t-r32-2-release-for-jetson-nano-jetson-tx1-tx2-and-jetson-agx-xavier/?offset=15#5369652, Manikanta said that it will be included in Jetpack 4.3.

So I want to know whether DMA is supported for “ethernet over PCIe” in JetPack 4.3.


Hi zhuce_cgf,

It is indeed available but only synchronous DMA operation is available at this point in time because of which the perf observed is less (around 300 Mbps).

What does synchronous DMA mean here? Will it effect the bandwidth in one side transfer?

Well, synchronous DMA means, SW fires up DMA once for every MTU of ethernet data. Asynchronous DMA means, SW can keep adding to DMA’s linked list and DMA keeps processing the list.
Yes. Synchronous DMA doesn’t give a very good performance.