File access in mounted volumes extremely slow, CPU bound

Docker Desktop
44

With Docker for mac:

docker version

Client:
Version: 1.11.1
API version: 1.23
Go version: go1.5.4
Git commit: 5604cbe
Built: Wed Apr 27 00:34:20 2016
OS/Arch: darwin/amd64

Server:
Version: 1.11.1
API version: 1.23
Go version: go1.5.4
Git commit: 8b63c77
Built: Tue May 10 10:39:20 2016
OS/Arch: linux/amd64

time dd if=/dev/zero of=test.dat bs=1024 count=100000

100000+0 records in
100000+0 records out
102400000 bytes (102 MB) copied, 38.0505 s, 2.7 MB/s
real 0m38.057s
user 0m0.170s
sys 0m2.030s

With Docker machine

time dd if=/dev/zero of=test.dat bs=1024 count=100000
100000+0 records in
100000+0 records out
102400000 bytes (102 MB) copied, 1.71642 s, 59.7 MB/s

real 0m1.721s
user 0m0.000s
sys 0m0.100s