fix #1546: usage percent may be rounded to 0 on Python 2.

2 files changed, 5 insertions, 4 deletions

diff --git a/HISTORY.rst b/HISTORY.rst
index 1f83b02c..733ab038 100644
--- a/HISTORY.rst
+++ b/HISTORY.rst
@@ -13,6 +13,7 @@ XXXX-XX-XX
   always turned into enums.
 - 1536_: [NetBSD] process cmdline() erroneously raise ZombieProcess error if
   cmdline has non encodable chars.
+- 1546_: usage percent may be rounded to 0 on Python 2.
 
 5.6.3
 =====
diff --git a/psutil/_common.py b/psutil/_common.py
index 4a006c1d..126d9d6f 100644
--- a/psutil/_common.py
+++ b/psutil/_common.py
@@ -266,12 +266,12 @@ if AF_UNIX is not None:
 def usage_percent(used, total, round_=None):
     """Calculate percentage usage of 'used' against 'total'."""
     try:
-        ret = (used / total) * 100
+        ret = (float(used) / total) * 100
     except ZeroDivisionError:
-        ret = 0.0 if isinstance(used, float) or isinstance(total, float) else 0
-    if round_ is not None:
-        return round(ret, round_)
+        return 0.0
     else:
+        if round_ is not None:
+            ret = round(ret, round_)
         return ret