fi_usnic(7) Libfabric Programmer's Manual
The usNIC Fabric Provider
The usnic provider is designed to run over the Cisco VIC (virtualized NIC) hardware on Cisco UCS servers. It utilizes the Cisco usNIC (userspace NIC) capabilities of the VIC to enable ultra low latency and other offload capabilities on Ethernet networks.
- The usnic libfabric provider requires the use of the “libnl”
- There are two versions of libnl generally available: v1 and v3; the usnic provider can use either version.
- If you are building libfabric/the usnic provider from source, you will need to have the libnl header files available (e.g., if you are installing libnl from RPM or other packaging system, install the “-devel” versions of the package).
- If you have libnl (either v1 or v3) installed in a non-standard
location (e.g., not in /usr/lib or /usr/lib64), you may need to
tell libfabric’s configure where to find libnl via the
--with-libnl=DIRcommand line option (where DIR is the installation prefix of the libnl package).
- The most common way to use the libfabric usnic provider is via an MPI implementation that uses libfabric (and the usnic provider) as a lower layer transport. MPI applications do not need to know anything about libfabric or usnic in this use case – the MPI implementation hides all these details from the application.
- If you are writing applications directly to the libfabric API:
- FI_EP_DGRAM endpoints are the best supported method of utilizing the usNIC interface. Specifically, the FI_EP_DGRAM endpoint type has been extensively tested as the underlying layer for Open MPI’s usnic BTL.
- FI_EP_MSG and FI_EP_RDM endpoints are implemented, but are only lightly tested. It is likely that there are still some bugs in these endpoint types. In particular, there are known bugs in RDM support in the presence of congestion or packet loss (issue 1621). RMA is not yet supported.
fi_provider(7) lists requirements for all providers. The following limitations exist in the usnic provider:
- multicast operations are not supported on FI_EP_DGRAM and FI_EP_RDM endpoints.
- FI_EP_MSG endpoints only support connect, accept, and getname CM operations.
- Passive endpoints only support listen, setname, and getname CM operations.
- FI_EP_DGRAM endpoints support
fi_recvmsg(), but some flags are ignored.
- Address vectors only support
- No counters are supported.
- The tag matching interface is not supported.
- FI_MSG_PREFIX is only supported on FI_EP_DGRAM and usage is limited to releases 1.1 and beyond.
- The usnic libfabric provider supports extensions that provide information and functionality beyond the standard libfabric interface. See the “USNIC EXTENSIONS” section, below.
The usnic libfabric provider exports extensions for additional VIC, usNIC, and Ethernet capabilities not provided by the standard libfabric interface.
These extensions are available via the “fi_ext_usnic.h” header file.
The following is an example of how to utilize the usnic “fabric getinfo”
extension, which returns IP and SR-IOV information about a usNIC
interface obtained from the
Note that other usnic extensions are defined for other fabric objects.
The second argument to
fi_open_ops(3) is used
to identify both the fid type and the extension family. For example,
FI_USNIC_AV_OPS_1 can be used in conjunction with an
to obtain usnic extensions for address vectors.
See fi_ext_usnic.h for more details.