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fi_verbs(7) Libfabric v1.15.1 fi_verbs(7) NAME fi_verbs - The Verbs Fabric Provider OVERVIEW The verbs provider enables applications using OFI to be run over any verbs hardware (Infiniband, iWarp, etc). It uses the Linux Verbs API for network transport and provides a translation of OFI calls to appro- priate verbs API calls. It uses librdmacm for communication management and libibverbs for other control and data transfer operations. REQUIREMENTS To successfully build and install verbs provider as part of libfabric, it needs the following packages: * libibverbs * libibverbs-devel * li- brdmacm * librdmacm-devel You may also want to look into any OS specific instructions for en- abling RDMA. e.g. RHEL has instructions on their documentation for en- abling RDMA. The IPoIB interface should be configured with a valid IP address. This is a requirement from librdmacm. SUPPORTED FEATURES The verbs provider supports a subset of OFI features. Endpoint types FI_EP_MSG, FI_EP_DGRAM (beta), FI_EP_RDM. FI_EP_RDM is supported via OFI RxM and RxD utility providers which are layered on top of verbs. To the app, the provider name string would appear as "verbs;ofi_rxm" or "verbs;ofi_rxd". Please refer the man pages for RxM (fi_rxm.7) and RxD (fi_rxd.7) to know about the capabili- ties and limitations for the FI_EP_RDM endpoint. Endpoint capabilities and features MSG endpoints FI_MSG, FI_RMA, FI_ATOMIC and shared receive contexts. DGRAM endpoints FI_MSG Modes Verbs provider requires applications to support the following modes: FI_EP_MSG endpoint type • FI_LOCAL_MR / FI_MR_LOCAL mr mode. • FI_RX_CQ_DATA for applications that want to use RMA. Applications must take responsibility of posting receives for any incoming CQ da- ta. Addressing Formats Supported addressing formats include * MSG and RDM (internal - depre- cated) EPs support: FI_SOCKADDR, FI_SOCKADDR_IN, FI_SOCKADDR_IN6, FI_SOCKADDR_IB * DGRAM supports: FI_ADDR_IB_UD Progress Verbs provider supports FI_PROGRESS_AUTO: Asynchronous operations make forward progress automatically. Operation flags Verbs provider supports FI_INJECT, FI_COMPLETION, FI_REMOTE_CQ_DATA, FI_TRANSMIT_COMPLETE. Msg Ordering Verbs provider support the following message ordering: • Read after Read • Read after Write • Read after Send • Write after Write • Write after Send • Send after Write • Send after Send and the following completion ordering: • TX contexts: FI_ORDER_STRICT • RX contexts: FI_ORDER_DATA Fork Verbs provider does not provide fork safety by default. Fork safety can be requested by setting IBV_FORK_SAFE, or RDMAV_FORK_SAFE. If the system configuration supports the use of huge pages, it is recommended to set RDMAV_HUGEPAGES_SAFE. See ibv_fork_init(3) for additional de- tails. Memory Registration Cache The verbs provider uses the common memory registration cache function- ality that's part of libfabric utility code. This speeds up memory registration calls from applications by caching registrations of fre- quently used memory regions. Please refer to fi_mr(3): Memory Regis- tration Cache section for more details. LIMITATIONS Memory Regions Only FI_MR_BASIC mode is supported. Adding regions via s/g list is supported only up to a s/g list size of 1. No support for binding mem- ory regions to a counter. Wait objects Only FI_WAIT_FD wait object is supported only for FI_EP_MSG endpoint type. Wait sets are not supported. Resource Management Application has to make sure CQs are not overrun as this cannot be de- tected by the provider. Unsupported Features The following features are not supported in verbs provider: Unsupported Capabilities FI_NAMED_RX_CTX, FI_DIRECTED_RECV, FI_TRIGGER, FI_RMA_EVENT Other unsupported features Scalable endpoints, FABRIC_DIRECT Unsupported features specific to MSG endpoints • Counters, FI_SOURCE, FI_TAGGED, FI_PEEK, FI_CLAIM, fi_cancel, fi_ep_alias, shared TX context, cq_readfrom operations. • Completion flags are not reported if a request posted to an endpoint completes in error. Fork The support for fork in the provider has the following limitations: • Fabric resources like endpoint, CQ, EQ, etc. should not be used in the forked process. • The memory registered using fi_mr_reg has to be page aligned since ibv_reg_mr marks the entire page that a memory region belongs to as not to be re-mapped when the process is forked (MADV_DONTFORK). XRC Transport The XRC transport is intended to be used when layered with the RXM provider and requires the use of shared receive contexts. See fi_rxm(7). To enable XRC, the following environment variables must usually be set: FI_VERBS_PREFER_XRC and FI_OFI_RXM_USE_SRX. RUNTIME PARAMETERS The verbs provider checks for the following environment variables. Common variables: FI_VERBS_TX_SIZE Default maximum tx context size (default: 384) FI_VERBS_RX_SIZE Default maximum rx context size (default: 384) FI_VERBS_TX_IOV_LIMIT Default maximum tx iov_limit (default: 4). Note: RDM (internal - deprecated) EP type supports only 1 FI_VERBS_RX_IOV_LIMIT Default maximum rx iov_limit (default: 4). Note: RDM (internal - deprecated) EP type supports only 1 FI_VERBS_INLINE_SIZE Default maximum inline size. Actual inject size returned in fi_info may be greater (default: 64) FI_VERBS_MIN_RNR_TIMER Set min_rnr_timer QP attribute (0 - 31) (default: 12) FI_VERBS_CQREAD_BUNCH_SIZE The number of entries to be read from the verbs completion queue at a time (default: 8). FI_VERBS_PREFER_XRC Prioritize XRC transport fi_info before RC transport fi_info (default: 0, RC fi_info will be before XRC fi_info) FI_VERBS_GID_IDX The GID index to use (default: 0) FI_VERBS_DEVICE_NAME Specify a specific verbs device to use by name Variables specific to MSG endpoints FI_VERBS_IFACE The prefix or the full name of the network interface associated with the verbs device (default: ib) Variables specific to DGRAM endpoints FI_VERBS_DGRAM_USE_NAME_SERVER The option that enables/disables OFI Name Server thread. The NS thread is used to resolve IP-addresses to provider specific ad- dresses (default: 1, if "OMPI_COMM_WORLD_RANK" and "PMI_RANK" environment variables aren't defined) FI_VERBS_NAME_SERVER_PORT The port on which Name Server thread listens incoming connec- tions and requests (default: 5678) Environment variables notes The fi_info utility would give the up-to-date information on environ- ment variables: fi_info -p verbs -e Troubleshooting / Known issues fi_getinfo returns -FI_ENODATA • Set FI_LOG_LEVEL=info or FI_LOG_LEVEL=debug (if debug build of lib- fabric is available) and check if there any errors because of incor- rect input parameters to fi_getinfo. • Check if "fi_info -p verbs" is successful. If that fails the follow- ing checklist may help in ensuring that the RDMA verbs stack is func- tional: • If libfabric was compiled, check if verbs provider was built. Building verbs provider would be skipped if its dependencies (list- ed in requirements) aren't available on the system. • Verify verbs device is functional: • Does ibv_rc_pingpong (available in libibverbs) test work? • Does ibv_devinfo (available in libibverbs) show the device with PORT_ACTIVE status? • Check if Subnet Manager (SM) is running on the switch or on one of the nodes in the cluster. • Is the cable connected? • Verify librdmacm is functional: • Does ucmatose test (available in librdmacm) work? • Is the IPoIB interface (e.g. ib0) up and configured with a valid IP address? Other issues When running an app over verbs provider with Valgrind, there may be re- ports of memory leak in functions from dependent libraries (e.g. libib- verbs, librdmacm). These leaks are safe to ignore. The provider protects CQ overruns that may happen because more TX oper- ations were posted to endpoints than CQ size. On the receive side, it isn't expected to overrun the CQ. In case it happens the application developer should take care not to post excess receives without draining the CQ. CQ overruns can make the MSG endpoints unusable. SEE ALSO fabric(7), fi_provider(7), AUTHORS OpenFabrics. Libfabric Programmer's Manual 2021-03-22 fi_verbs(7)
NAME | OVERVIEW | REQUIREMENTS | SUPPORTED FEATURES | LIMITATIONS | RUNTIME PARAMETERS | Troubleshooting / Known issues | SEE ALSO | AUTHORS
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