copy!(dst, src) and copyto!(dst, src) are significantly slower and allocate more memory than copyto!(dest, do, src, so[, N])

[colinxs]

I ran into some odd behavior today. Not quite sure what's going on so I thought I'd leave this here.

Cheers!

Describe the bug
copy!(dst, src) and copyto!(dst, src) are significantly slower and allocate more memory than copyto!(dest, do, src, so[, N])

To Reproduce

julia> CuArrays.allowscalar(false);                                                                         
julia> const x=rand(Float32, 1000,1000);
julia> const xc=cu(x);
julia> @btime @inbounds copyto!($xc, 1, $x, 1, length($x));                                       
  353.422 μs (3 allocations: 64 bytes)                                                                                                                                                    
julia> @btime @inbounds copyto!($xc, 1, $x, 1);                                                  
  353.290 μs (3 allocations: 64 bytes)                                                                                                                                                            
julia> @btime @inbounds copyto!($xc, $x);                                                        
  584.373 μs (5 allocations: 3.81 MiB)                                                                                                                
julia> @btime @inbounds copy!($xc, $x);                                                          
  581.387 μs (5 allocations: 3.81 MiB)                                                           

Expected behavior
For Array, there is virtually no speed or allocation between any of the above variations. I would expect the same for CuArray.

Build log
(don't know why it failed, I'll take a look at some point)

Could not find library 'cudnn'.

CuArrays.jl has been built successfully, but there were warnings.
Some functionality may be unavailable.

Environment details (please complete this section)
Details on Julia:

Julia Version 1.1.1
Commit 55e36cc308 (2019-05-16 04:10 UTC)
Platform Info:
  OS: Linux (x86_64-pc-linux-gnu)
  CPU: Intel(R) Core(TM) i7-8850H CPU @ 2.60GHz
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-6.0.1 (ORCJIT, skylake)
Environment:
  JULIA_NUM_THREADS = 6

Julia packages:

• CuArrays.jl: 1.0.2
• CUDAnative.jl: 2.2.0
• CUDAdrv.jl: 3.0.1

nvcc --version
nvcc: NVIDIA (R) Cuda compiler driver
Copyright (c) 2005-2019 NVIDIA Corporation
Built on Fri_Feb__8_19:08:17_PST_2019
Cuda compilation tools, release 10.1, V10.1.105

Additional context

[maleadt]

I don't see a difference anymore on current CUDA.jl:

julia> @btime @inbounds copyto!($xc, 1, $x, 1, length($x));
  187.309 μs (5 allocations: 80 bytes)

julia> @btime @inbounds copyto!($xc, 1, $x, 1);
  193.229 μs (5 allocations: 80 bytes)

julia> @btime @inbounds copyto!($xc, $x);
  195.369 μs (5 allocations: 80 bytes)

julia> @btime @inbounds copy!($xc, $x);
  200.839 μs (5 allocations: 80 bytes)