[libfabric-users] Verbs provider not permitting FI_EP_MSG

Steve Welch swelch at systemfabricworks.com
Thu Jan 16 08:03:58 PST 2020

Hi Phillip,

Since you are specifying an FI_EP_RDM in your hints I assume you want to utilize the RXM provider on top of the Verbs core provider (i.e. ofi_rxm;verbs). The Verbs provider does not offer native FI_RDM_EP support. To use either XRC (or FI_EP_RDM endpoint)  you will have to use RXM, but I am unaware of any IB provider that supported XRC that did not support RC.

If you issue a 'fi_info -p verbs -v’ it will list all the verbs domains supported and the underlying protocol and you could verify if RC should be supported (via RXM for FI_EP_RDM). If you issue 'fi_info -p “ofi_rxm;verbs”', you should see multiple domains for the “ofi_rxm;verbs” provider combination. XRC domains have the “-xrc” suffix.

If you must use XRC and the RXM/Verbs combination then you will need to set the environment variable FI_OFI_RXM_USE_SRX=1 and RXM will handle the shared RX details.


> On Jan 16, 2020, at 8:56 AM, Philip Davis <philip.e.davis at rutgers.edu> wrote:
> Hello,
> I am working with a user that is running on an older Infiniband cluster. Using libfaric with the following hints:
> hints->caps = FI_MSG | FI_SEND | FI_RECV | FI_REMOTE_READ |
>                  FI_REMOTE_WRITE | FI_RMA | FI_READ | FI_WRITE;
>                  FI_ASYNC_IOV | FI_RX_CQ_DATA;
>    hints->domain_attr->mr_mode = FI_MR_BASIC;
>    hints->domain_attr->control_progress = FI_PROGRESS_AUTO;
>    hints->domain_attr->data_progress = FI_PROGRESS_AUTO;
>    hints->ep_attr->type = FI_EP_RDM;
> No verbs providers are found. Looking through the debug output, I suspect this is the crucial line:
> libfabric:verbs:fabric:fi_ibv_get_matching_info():1213<info> hints->ep_attr->rx_ctx_cnt != FI_SHARED_CONTEXT. Skipping XRC FI_EP_MSG endpoints
> I take it that the underlying hardware is only compatible with FI_PROTO_RDMA_CM_IB_XRC protocol for MSG endpoints, and it looks like I need to have FI_SHARED_CONTEXT enabled for these endpoints to be supported. I’m having some trouble understanding the implications of using FI_SHARED_CONTEXT. If I only ever use one endpoint, is there any functional or performance impact to setting this? I’d rather not change to using shared contexts unconditionally, so is there a good way for me to detect this situation other than to do a maximally permissive fi_getinfo and iterate through the verbs results?
> Thanks,
> Philip
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