While copying  (right clicked to select in one folder and pasted into another folder using dolphin) a ~450GB folder from an 500GB exfat external drive to a local 1TB ext4 drive on my machine, the KIO_file was using 100% of my CPU. I was monitoring CPU usage using top and KIO_file usage stayed below ~70 for most of the operation. During the last ~20min or so the CPU stayed between 99% and 100% with brief spikes from 120% to 175%. 

The system did not crash, it only became less responsive. I was looking for ways to optimize file copying operations and did not find any. I am new to KDE so if this is in the wrong place let me know please.

Reproducible: Didn't try

Steps to Reproduce:
1. right click to select in one folder and pasted into another folder using dolphin
2. run top and monitor progress

Actual Results:  
>=99% CPU usage by KIO_file

Expected Results:  
<99% CPU usage by KIO_file

System Notes:
AMD FX8320 3.5Ghz 8core CPU
16GB Ram
Description:    Linux Mint 17.3 Rosa
Release:        17.3
Codename:       rosa
(The Version list of choices was only up to 4.14.1)
KDE Development Platform: 4.14.2
Operating System: Ubuntu 14.04.3 LTS (Linux Mint KDE)
Kernel: Linux 3.19.0-32-generic
Architecture: x86_64