title: Sometimes pip install is very slow
body: <p>I am sure it is not network issue. Some of my machine install packages using pip is very fast while some other machine is pretty slow, from the logs, I suspect the slow is due to it will compile the package, I am wondering how can I avoid this compilation to make the pip installation fast. Here's the logs from the slow pip installation.</p>
  
  <pre><code>Collecting numpy==1.10.4 (from -r requirements.txt (line 1))
    Downloading numpy-1.10.4.tar.gz (4.1MB)
      100% |████████████████████████████████| 4.1MB 95kB/s
  Requirement already satisfied (use --upgrade to upgrade): wheel==0.26.0 in ./lib/python2.7/site-packages (from -r requirements.txt (line 2))
  Building wheels for collected packages: numpy
    Running setup.py bdist_wheel for numpy ... -
  done
    Stored in directory: /root/.cache/pip/wheels/66/f5/d7/f6ddd78b61037fcb51a3e32c9cd276e292343cdd62d5384efd
  Successfully built numpy
  </code></pre>