On Tue, Apr 04, 2017 at 04:38:40PM +0300, Marcel Apfelbaum wrote: > Here are some thoughts regarding the Soft RoCE usage in our project. > We thought about using it as backend for QEMU pvrdma device > we didn't how it will support our requirements. > > 1. Does Soft RoCE support inter process (VM) fast path ? The KDBR > removes the need for hw resources, emulated or not, concentrating > on one copy from a VM to another. I'd rather see someone optimize the loopback path of soft roce than see KDBR :) > 3. Our intention is for KDBR to be used in other contexts as well when we need > inter VM data exchange, e.g. backend for virtio devices. We didn't see how this > kind of requirement can be implemented inside SoftRoce as we don't see any > connection between them. KDBR looks like weak RDMA to me, so it is reasonable question why not use full RDMA with loopback optimization instead of creating something unique. IMHO, it also makes more sense for something like KDBR to live as a RDMA transport, not as a unique char device, it is obviously very RDMA-like. .. and the char dev really can't be used when implementing user space RDMA, that would just make a big mess.. > 4. We don't want all the VM memory to be pinned since it disable memory-over-commit > which in turn will make the pvrdma device useless. > We weren't sure how nice would play Soft RoCE with memory pinning and we wanted > more control on memory management. It may be a solvable issue, but combined > with the others lead us to our decision to come up with our kernel bridge (char soft roce certainly can be optimized to remove the page pin and always run in an ODP-like mode. But obviously if you connect pvrdma to real hardware then the page pin comes back. > device or not, we went for it since it was the easiest to > implement for a POC) I can see why it would be easy to implement, but not sure how this really improves the kernel.. Jason -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
