NAME¶

fi_sockets - The Sockets Fabric Provider

OVERVIEW¶

The sockets provider is a general purpose provider that can be used on any system that supports TCP sockets. The provider is not intended to provide performance improvements over regular TCP sockets, but rather to allow developers to write, test, and debug application code even on platforms that do not have high-performance fabric hardware. The sockets provider supports all libfabric provider requirements and interfaces.

SUPPORTED FEATURES¶

The sockets provider supports all the features defined for the libfabric API. Key features include:

Endpoint types

The provider supports all endpoint types: FI_EP_MSG, FI_EP_RDM, and FI_EP_DGRAM.

Endpoint capabilities

The following data transfer interface is supported for a all endpoint types: fi_msg. Additionally, these interfaces are supported for reliable endpoints (FI_EP_MSG and FI_EP_RDM): fi_tagged, fi_atomic, and fi_rma.

Modes

The sockets provider supports all operational modes including FI_CONTEXT and FI_MSG_PREFIX.

Progress

Sockets provider supports both FI_PROGRESS_AUTO and FI_PROGRESS_MANUAL, with a default set to auto. When progress is set to auto, a background thread runs to ensure that progress is made for asynchronous requests.

LIMITATIONS¶

Sockets provider attempts to emulate the entire API set, including all defined options. In order to support development on a wide range of systems, it is implemented over TCP sockets. As a result, the performance numbers are lower compared to other providers implemented over high-speed fabric, and lower than what an application might see implementing to sockets directly.

Does not support FI_ADDR_STR address format.

RUNTIME PARAMETERS¶

The sockets provider checks for the following environment variables -

FI_SOCKETS_PE_WAITTIME

An integer value that specifies how many milliseconds to spin while waiting for progress in FI_PROGRESS_AUTO mode.

FI_SOCKETS_CONN_TIMEOUT

An integer value that specifies how many milliseconds to wait for one connection establishment.

FI_SOCKETS_MAX_CONN_RETRY

An integer value that specifies the number of socket connection retries before reporting as failure.

FI_SOCKETS_DEF_CONN_MAP_SZ

An integer to specify the default connection map size.

FI_SOCKETS_DEF_AV_SZ

An integer to specify the default address vector size.

FI_SOCKETS_DEF_CQ_SZ

An integer to specify the default completion queue size.

FI_SOCKETS_DEF_EQ_SZ

An integer to specify the default event queue size.

FI_SOCKETS_DGRAM_DROP_RATE

An integer value to specify the drop rate of dgram frame when endpoint is FI_EP_DGRAM. This is for debugging purpose only.

FI_SOCKETS_PE_AFFINITY

If specified, progress thread is bound to the indicated range(s) of Linux virtual processor ID(s). This option is currently not supported on OS X. The usage is - id_start[-id_end[:stride]][,].

FI_SOCKETS_KEEPALIVE_ENABLE

A boolean to enable the keepalive support.

FI_SOCKETS_KEEPALIVE_TIME

An integer to specify the idle time in seconds before sending the first keepalive probe. Only relevant if FI_SOCKETS_KEEPALIVE_ENABLE is enabled.

FI_SOCKETS_KEEPALIVE_INTVL

An integer to specify the time in seconds between individual keepalive probes. Only relevant if FI_SOCKETS_KEEPALIVE_ENABLE is enabled.

FI_SOCKETS_KEEPALIVE_PROBES

An integer to specify the maximum number of keepalive probes sent before dropping the connection. Only relevant if FI_SOCKETS_KEEPALIVE_ENABLE is enabled.

FI_SOCKETS_IFACE

The prefix or the name of the network interface (default: any)

LARGE SCALE JOBS¶

For large scale runs one can use these environment variables to set the default parameters e.g. size of the address vector(AV), completion queue (CQ), connection map etc. that satisfies the requirement of the particular benchmark. The recommended parameters for large scale runs are FI_SOCKETS_MAX_CONN_RETRY, FI_SOCKETS_DEF_CONN_MAP_SZ, FI_SOCKETS_DEF_AV_SZ, FI_SOCKETS_DEF_CQ_SZ, FI_SOCKETS_DEF_EQ_SZ.

SEE ALSO¶

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

AUTHORS¶

OpenFabrics.