Libfabric Programmer's Manual

fi_rxm(7) Libfabric Programmer's Manual

NAME

The RxM (RDM over MSG) Utility Provider

OVERVIEW

The RxM provider (ofi_rxm) is an utility provider that supports RDM endpoint emulated over MSG endpoint of a core provider.

REQUIREMENTS

RxM provider requires the core provider to support the following features:

  • MSG endpoints (FI_EP_MSG)

  • Shared receive contexts (FI_SHARED_CONTEXT)

  • RMA read/write (FI_RMA)

  • FI_OPT_CM_DATA_SIZE of atleast 24 bytes

SUPPORTED FEATURES

The RxM provider currently supports FI_MSG, FI_TAGGED and FI_RMA capabilities.

Endpoint types
The provider supports only FI_EP_RDM.
Endpoint capabilities
The following data transfer interface is supported: FI_MSG, FI_TAGGED, FI_RMA.
Progress
The RxM provider supports only FI_PROGRESS_MANUAL for now.
Addressing Formats
FI_SOCKADDR, FI_SOCKADDR_IN
Memory Region
FI_MR_VIRT_ADDR, FI_MR_ALLOCATED, FI_MR_PROV_KEY MR mode bits would be required from the app in case the core provider requires it.

LIMITATIONS

When using RxM provider, some limitations from the underlying MSG provider could also show up. Please refer to the corresponding MSG provider man pages to find about those limitations.

Unsupported features

RxM provider does not support the following features:

  • op_flags: FI_CLAIM, FI_PEEK, FI_FENCE.

  • FI_ATOMIC

  • Scalable endpoints

  • Shared contexts

  • FABRIC_DIRECT

  • Multi recv

  • Counters

  • FI_MR_SCALABLE

  • Authorization keys

  • Application error data buffers

  • Multicast

  • FI_ADDR_STR, FI_SYNC_ERR

  • Reporting unknown source addr data as part of completions

  • Triggered operations

  • fi_cq_sread, fi_cq_sreadfrom and fi_cq_signal calls.

Auto progress

When sending large messages, an app doing an sread or waiting on the CQ file descriptor may not get a completion when reading the CQ after being woken up from the wait. The app has to do sread or wait on the file descriptor again.

Usage limitations

RxM provider should work fine for client - server programs like fabtests. Support for MPI, SHMEM and other applications is work in progress.

Known failures in ofiwg/fabtests

  • fi_rdm_tagged_peek

HW Specific

iWARP

  • fi_poll -t queue
  • fi_rma_bw -e rdm -o write
  • fi_rma_bw -e rdm -o writedata
  • fi_rdm_rma -o writedata

RUNTIME PARAMETERS

No runtime parameters are currently defined.

SEE ALSO

fabric(7), fi_provider(7), fi_getinfo(3)