Messages in this thread | | | Date | Thu, 28 Sep 2023 05:16:10 +0200 | Subject | Re: [PATCH net-next v4 09/18] net/smc: introduce SMC-D loopback device | From | Jan Karcher <> |
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On 26/09/2023 09:24, Alexandra Winter wrote: > > > On 25.09.23 17:18, Dust Li wrote: >>> Hello Wen Gu, >>> >>> thank you for adding the Kconfig, so the distributions can decide when to offer this feature. >>> >>> I propose you add some kind of runtime switch as well. Not every user who loads the SMC module >>> may want to exploit smcd-loopback. Especially in native environements without containers. >>> >>> If no RoCE interfaces or no ISM interfaces exist, the respective handling is skipped in SMC. >>> If loopback is always created unconditionally, there is no way to opt-out. >> Hi Sandy, >> >> After talking to Wen Gu offline, I think the real issue here might be >> we don't have an abstract layer in SMC, something like net/core/dev.c >> >> Without this, we cannot do: >> >> 1. Enable/disable those devices dynamically >> Currently, If we want to disable a SMC-R device to communicate with >> others, we need to refer to 'ip link set dev xxx down' to disable the >> netdevice, then Infiniband subsystem will notify SMC that the state of >> the IB device has changed. We cannot explicitly choose not to use some >> specific IB/RoCE devices without disable totally. >> If the loopback device need to support enable/disable itself, I >> think it might be better to enable this feature for all SMC devices. >> >> 2. Do statistics per device >> Now, we have to relay on IB/RoCE devices' hardware statistics to see >> how many packets/bytes we have sent through this device. >> >> Both the above issues get worse when the IB/RoCE device is shared by SMC >> and userspace RDMA applications. If SMC-R and userspace RDMA applications >> run at the same time, we can't enable the device to run userspace RDMA >> applications while block it from running SMC. For statistics, we cannot >> tell how many packets/bytes were sent by SMC and how many were sent by >> userspace RDMA applications. >> >> So I think those are better to support in the SMC layer. >> >> Best regards! >> Dust > > Thank you very much for your considerations. I also think a generic handling > of these requirements in the smc layer would be best. Especially, if we want > to add virtio-ism support soon. There we will face the same issues again. > Let's hear what others think about this. > >
Thanks you Sandy for bringing it up and Dust Li & Wen Gu for your thoughts. I agree that such a runtime switch is needed and also that this generic handling would be good in the smc layer.
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