title: numpy.recfromcsv not releasing GIL
body: <p>I am using numpy.recfromcsv function to read a large amount of data. This is done in a worker thread so that my GUI (PySide) thread is not blocked. Even though I know of GIL that ensures that only one thread is being interpreted by Python at a time, I had very good experience with numpy operations. Most of them seem to release GIL so that while other processor cores are working on a numpy operation, my GUI thread remains responsive.</p>
  
  <p>However numpy.recfromcsv causes my GUI to become sluggish. Does that mean that it does not release GIL? Or is there another reason? Is there a workaround to keep the GUI responsive even during this operation? I tried multiprocessing by this seems to be overkill and incredible pain with sharing or pickling large amounts of data.</p>