I'm also having this problem copying to an external USB 3 drive, with Nemo (Cinnamon file manager) copies around 35 MiB/s on my Q6600 CPU. big_writes helped, but although file copying via Nemo sped up to around 60 MiB/s, it was still CPU bound. Copying via pv < source_file > dest_file is faster and not CPU bound, around 130 MiB/s. pv without big writes is CPU bound at 90 MiB/s, so Nemo seems to be the main culprit in my case.
This is in Xenial Xerus (development branch) 16.04 64-bit.
I'm also having this problem copying to an external USB 3 drive, with Nemo (Cinnamon file manager) copies around 35 MiB/s on my Q6600 CPU. big_writes helped, but although file copying via Nemo sped up to around 60 MiB/s, it was still CPU bound. Copying via pv < source_file > dest_file is faster and not CPU bound, around 130 MiB/s. pv without big writes is CPU bound at 90 MiB/s, so Nemo seems to be the main culprit in my case.
This is in Xenial Xerus (development branch) 16.04 64-bit.