Performance reduces with nodatasum

Hello,
apparently I have found an issue with btrfs: performance reduces with nodatasum and multi-device "raid0" or "single".

I was testing with a series of 8 LIO ramdisks, with btrfs on those in multi-device single mode, and writing zeroes on the filesystem with 16 dd in parallel. Performance decreases significantly if the filesystem is mounted with nodatasum, or with nodatacow which implies nodatasum.
CPU occupation also reduces, together with speed, as seen with htop.

At first I thought it was my problem, but then I saw this web page
http://www.linux-mag.com/id/7308/3/
which also reports reduced performance with nodatasum and multi-device raid0 or single, e.g. see these two lines:

Btrfs
two disks,
single
standard
50.144 50.264 126.984 131.130

Btrfs
two disks,
single
nodatacow,
nodatasum
43.834 47.603 131.612 131.470

similarly with raid0

even more with compression:

Btrfs
two disks,
raid0
-o compress
70.234 69.048 130.852 129928
Btrfs

two disks,
raid0
-o compress
nodatacow,
nodatasum
48.762 48.831 130.812 130.202

If you go higher with the performances, such as with ramdisks, in the GB/sec range, it reduces more than that. I have noticed upto 50% reduction.

It would be important to fix this problem for high-performance usages of btrfs.

Best regards
BM

Sorry I forgot to mention the kernel version: 3.14.19 not tested with higher versions

I just noticed that the page I have linked which also reports the problem
http://www.linux-mag.com/id/7308/3/
is dated April 21st, 2009 , with kernel version 2.6.30-rc1
so this problem is not a recent regression but has been there probably since always. So it's likely that it's present also in latest 3.17-rc7 even if I can't check right now. Best regards
BM