fi_verbs(7) @VERSION@ fi_verbs(7)NAMEfi_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.
SUPPORTED FEATURES
The verbs provider supports a subset of OFI features.
Endpoint types
FI_EP_MSG, FI_EP_RDM (Experimental support FI_MSG, FI_TAGGED, FI_RMA
interfaces).
Endpoint capabilities and features
MSG endpoints
FI_MSG, FI_RMA, FI_ATOMIC and shared receive contexts.
RDM endpoints
FI_MSG, FI_TAGGED, FI_RMA
Modes
Verbs provider requires applications to support the following modes:
· FI_LOCAL_MR for all applications.
· FI_RX_CQ_DATA for applications that want to use RMA. Applications
must take responsibility of posting receives for any incoming CQ
data.
· FI_CONTEXT for applications making uses of the experimental FI_EP_RDM
capability.
Addressing Formats
Supported addressing formats include FI_SOCKADDR, FI_SOCKADDR_IN,
FI_SOCKADDR_IN6, FI_SOCKADDR_IB
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 supports the fork system call by default. See the limi‐
tations section for restrictions. It can be turned off by setting the
FI_FORK_UNSAFE environment variable to "yes". This can improve the
performance of memory registrations but it also makes the use of fork
unsafe.
LIMITATIONS
Memory Regions
Only FI_MR_BASIC mode is supported. Adding regions via s/g list is
supported only up to s/g list size of 1. No support for binding memory
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
detected by the provider.
Unsupported Features
The following features are not supported in verbs provider:
Unsupported Endpoint types
FI_EP_DGRAM
Unsupported Capabilities
FI_NAMED_RX_CTX, FI_DIRECTED_RECV, FI_TRIGGER, FI_MULTI_RECV,
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.
Unsupported features specific to RDM endpoints
The RDM support for verbs have the following limitations:
· Supports iovs of only size 1.
· Wait objects are not supported.
· Not thread safe.
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).
RUNTIME PARAMETERS
The verbs provider checks for the following environment variables.
Variables specific to MSG endpoints
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)
FI_VERBS_RX_IOV_LIMIT : Default maximum rx iov_limit (default: 4)
Variables specific to RDM endpoints
FI_VERBS_IFACE : The prefix or the full name of the network interface
associated with the IB device (default: ib)
FI_VERBS_RDM_BUFFER_NUM : The number of pre-registered buffers for
buffered operations between the endpoints, must be a power of 2
(default: 8).
FI_VERBS_RDM_BUFFER_SIZE : The maximum size of a buffered operation
(bytes) (default: platform specific).
FI_VERBS_RDM_RNDV_SEG_SIZE : The segment size for zero copy protocols
(bytes)(default: 1073741824).
FI_VERBS_RDM_CQREAD_BUNCH_SIZE : The number of entries to be read from
the verbs completion queue at a time (default: 8).
FI_VERBS_RDM_THREAD_TIMEOUT : The wake up timeout of the helper thread
(usec) (default: 100).
FI_VERBS_RDM_EAGER_SEND_OPCODE : The operation code that will be used
for eager messaging. Only IBV_WR_SEND and IBV_WR_RDMA_WRITE_WITH_IMM
are supported. The last one is not applicable for iWarp. (default:
IBV_WR_SEND)
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
When running an app over verbs provider with valgrind, there may be
reports of memory leak in functions from dependent libraries (e.g.
libibverbs, librdmacm). These leaks are safe to ignore.
SEE ALSOfabric(7), fi_provider(7),
AUTHORS
OpenFabrics.
Libfabric Programmer's Manual 2017-07-24 fi_verbs(7)
