> The operation of copying data is super easy to parallelize across multiple threads. […] This will make the copy super-fast especially if the CPU has a large core count.

I seriously doubt that. Unless you have a NUMA system, a single core in a desktop CPU can easily saturate the bandwidth of the system RAM controller. If you can avoid going through main memory – e.g., when copying between the L2 caches of different cores – multi-threading can speed things up. But then you need precise knowledge of your program's memory access behavior, and this is outside the scope of a general-purpose memcpy.