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Yossi Itigin edited this page Jul 27, 2015 · 2 revisions

UCX code consists of 3 parts:

  • Protocol Layer - UCP
  • Transport Layer - UCT
  • Services - UCS

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Protocol Layer

Supports all functionality described in the API, and does not require knowledge of particular hardware. It would try to provide best "out-of-box" performance, combining different hardware mechanisms and transports. It may emulate features which are not directly supported in hardware, such as one-sided operations. In addition, it would support common software protocols which are not implemented in hardware, such as tag matching and generic active messages. More details here

Transport Layer

Provides direct access to hardware capabilities, without decision logic which would prefer one hardware mechanism over another. Some functionality may not be supported, due to hardware limitations. The capabilities are exposed in the interface.
More details here.

Services

Collection of generic services, data structures, debug aids, etc.

Responsibilities of each layer

What Where Why
Tag matching High level Software protocol
RMA/AMO emulation High level Software protocol
Fragmentation High level Software protocol
Pending queue High level Stateful
Multi-transport/channel/rail High level OOB optimization
Select inline/bcopy/zcopy High level optimization logic
Reliability (e.g UD) Low level Transport specific
DMA buffer ownership Low level Transport specific
Memory registration cache Low level Transport dependent

See also:

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