On Fri, 5 Sep 2025 11:00:59 +0200 Halil Pasic <pasic@xxxxxxxxxxxxx> wrote: > > 1. What if the two sides have different max_send_wr/max_recv_wr configurations? > > IIUC, For example, if the client sets max_send_wr to 64, but the server sets > > max_recv_wr to 16, the client might overflow the server's QP receive > > queue, potentially causing an RNR (Receiver Not Ready) error. > > I don't think the 16 is spec-ed anywhere and if the client and the server > need to agree on the same value it should either be speced, or a > protocol mechanism for negotiating it needs to exist. So what is your > take on this as an SMC maintainer? > > I think, we have tested heterogeneous setups and didn't see any grave > issues. But let me please do a follow up on this. Maybe the other > maintainers can chime in as well. Did some research and some thinking. Are you concerned about a performance regression for e.g. 64 -> 16 compared to 16 -> 16? According to my current understanding the RNR must not lead to a catastrophic failure, but the RDMA/IB stack is supposed to handle that. I would like to also point out that bumping SMC_WR_BUF_CNT basically has the same problem, although admittedly to a smaller extent because it is only between "old" and "new". Assuming that my understanding is correct, I believe that the problem of the potential RNR is inherent to the objective of the series, and probably one that can be lived with. Given this entire EID business, I think the SMC-R setup is likely to happen in a coordinated fashion for all potential peers, and I hope whoever tweaks those values has a sufficent understanding or empiric evidence to justify the tweaks. Assuming my understanding is not utterly wrong, I would very much like to know what would you want me to do with this? Thank you in advance! Regards, Hali
