Blind Physical DMA (Continued)

• Communication Assist is set of DMA engines attached to memory bus

• Specify Physical Address to Comm Assist

  • sender and receiver

• DMA engine is given pointer to Physical Address and starts transfer when message arrives

  • Is msg for OS or user? which user?

• Can support MP abstraction in OS, perform “interpretation”, tag match, dispatch, and buffering.

  • Remote Read, Remote Queues

• When to Copy to User Space?

  • DMA->kernel buffer->user space
  • DMA->user space

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