multiprocessing won't utilize all of platform resources

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2018-03-28.14:56:29.127>
labels = ['type-bug', 'OS-windows']
title = "multiprocessing won't utilize all of platform resources"
updated_at = <Date 2018-03-28.14:56:29.127>
user = 'https://bugs.python.org/yanirh'

bugs.python.org fields:

activity = <Date 2018-03-28.14:56:29.127>
actor = 'yanirh'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Windows']
creation = <Date 2018-03-28.14:56:29.127>
creator = 'yanirh'
dependencies = []
files = []
hgrepos = []
issue_num = 33171
keywords = []
message_count = 1.0
messages = ['314600']
nosy_count = 5.0
nosy_names = ['paul.moore', 'tim.golden', 'zach.ware', 'steve.dower', 'yanirh']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue33171'
versions = ['Python 3.6']