Docker use only 4 vCPU, not 8

Expected behavior

pinata list return hypervisor = native (memory=4, ncpu=8)

Actual behavior

pinata list return hypervisor = native (memory=4, ncpu=4)

Information

sysctl -n machdep.cpu.brand_string
Intel(R) Core(TM) i7-4770HQ CPU @ 2.20GHz
> getconf _NPROCESSORS_ONLN
8
> pinata diagnose -u
OS X: version 10.11.1 (build: 15B42)
Docker.app: version v1.11.0-beta8.2
Running diagnostic tests:
[OK]      docker-cli
[OK]      Moby booted
[OK]      driver.amd64-linux
[OK]      vmnetd
[OK]      osxfs
[OK]      db
[OK]      slirp
[OK]      menubar
[OK]      environment
[OK]      Docker
[OK]      VT-x
Docker logs are being collected into /tmp/20160426-144540.tar.gz
Most specific failure is: No error was detected
Your unique id is: 8A30D5B0-63BE-434B-972F-788E2BBAF531