Re. #1210: add doc warning explaining that cpu_times() values can som…

…etimes go backwards

Signed-off-by: Giampaolo Rodola <g.rodola@gmail.com>

README.rst

@@ -299,9 +299,9 @@ Process management
     >>> p
     psutil.Process(pid=7055, name='python3', status='running', started='09:04:44')
     >>> p.name()
-    'python'
+    'python3'
     >>> p.exe()
-    '/usr/bin/python'
+    '/usr/bin/python3'
     >>> p.cwd()
     '/home/giampaolo'
     >>> p.cmdline()
@@ -444,23 +444,6 @@ Further process APIs
     >>> gone, alive = psutil.wait_procs(procs_list, timeout=3, callback=on_terminate)
     >>>
 
-Popen wrapper:
-
-.. code-block:: python
-
-    >>> import psutil
-    >>> from subprocess import PIPE
-    >>> p = psutil.Popen(["/usr/bin/python", "-c", "print('hello')"], stdout=PIPE)
-    >>> p.name()
-    'python'
-    >>> p.username()
-    'giampaolo'
-    >>> p.communicate()
-    ('hello\n', None)
-    >>> p.wait(timeout=2)
-    0
-    >>>
-
 Windows services
 ----------------
 

docs/index.rst

@@ -144,6 +144,12 @@ CPU
 
   .. versionchanged:: 4.1.0 added *interrupt* and *dpc* fields on Windows.
 
+    .. warning::
+      CPU times are always supposed to increase over time, or at least remain
+      the same, and that's because time cannot go backwards.
+      Surprisingly sometimes this might not be the case (at least on Windows
+      and Linux), see `#1210 <https://github.com/giampaolo/psutil/issues/1210#issuecomment-363046156>`__.
+
 .. function:: cpu_percent(interval=None, percpu=False)
 
   Return a float representing the current system-wide CPU utilization as a

psutil/__init__.py

@@ -1724,7 +1724,6 @@ def cpu_percent(interval=None, percpu=False):
 
     def calculate(t1, t2):
         times_delta = _cpu_times_deltas(t1, t2)
-
         all_delta = _cpu_tot_time(times_delta)
         busy_delta = _cpu_busy_time(times_delta)