Tested on my system a fast drive : nvme ssd.
ll test.mkv
.rw-rw-r-- 4,3G meven 30 oct. 16:16 test.mkv
Before:
time KDE_FORK_SLAVES=1 /usr/bin/kioclient5 cp file:///home/meven/test.mkv file:///home/meven/testa.mkv
real 0m19,583s
user 0m0,084s
sys 0m0,060s
After:
time KDE_FORK_SLAVES=1 /home/meven/kde/usr/bin/kioclient5 cp file:///home/meven/test.mkv file:///home/meven/testa.mkv
real 0m18,488s
user 0m0,075s
sys 0m0,046s
For reference cp:
time cp test.mkv testa.mkv
real 0m18,707s
user 0m0,062s
sys 0m7,017s
We can be as fast as cp with this, a 5.5% spead increase of large file copy.
Results depend on your system.