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While profiling application with nvprof I found both PtoP and DtoD memcpy. I am not sure about the difference between these two.

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einpoklum
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Saiful
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1 Answers1

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Device to device (DtoD) is a copy within a single GPU.
Peer to Peer (PtoP) is from one GPU to another.

The latter only happens in multi-GPU systems.

And for other transfers host refers to CPU, device refers to GPU.

The naming device to device transfer predates a lot of the work on multiple GPUs, otherwise the naming might have been a little different.

Jonathan Olson
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    I ran the application in a multi-GPU system. I found that the DtoD copy has a BW utilization of ~80 GB/s while PtoP copy needed 4 GB/s in a system with PCIe interconnect. Hence, the DtoD copy has to be within the same device. – Saiful Jul 16 '17 at 00:10