fix #1277 / osx / virtual_memory: 'available' and 'used' memory were not calculated properly

4 files changed, 14 insertions, 11 deletions

diff --git a/HISTORY.rst b/HISTORY.rst
index 735b9345..4b2e7ed2 100644
--- a/HISTORY.rst
+++ b/HISTORY.rst
@@ -16,6 +16,8 @@ XXXX-XX-XX
 **Bug fixes**
 
 - 715_: do not print exception on import time in case cpu_times() fails.
+- 1277_: [OSX] available and used memory (psutil.virtual_memory()) metrics are
+  not accurate.
 - 1294_: [Windows] psutil.Process().connections() may sometimes fail with
   intermittent 0xC0000001.  (patch by Sylvain Duchesne)
 - 1320_: [AIX] system CPU times (psutil.cpu_times()) were being reported with
diff --git a/psutil/_psosx.py b/psutil/_psosx.py
index fbfedf3e..94e22bc7 100644
--- a/psutil/_psosx.py
+++ b/psutil/_psosx.py
@@ -119,9 +119,16 @@ pmmap_ext = namedtuple(
 
 def virtual_memory():
     """System virtual memory as a namedtuple."""
-    total, active, inactive, wired, free = cext.virtual_mem()
+    total, active, inactive, wired, free, speculative = cext.virtual_mem()
+    # This is how Zabbix calculate avail and used mem:
+    # https://github.com/zabbix/zabbix/blob/trunk/src/libs/zbxsysinfo/
+    #     osx/memory.c
+    # Also see: https://github.com/giampaolo/psutil/issues/1277
     avail = inactive + free
-    used = active + inactive + wired
+    used = active + wired
+    # This is NOT how Zabbix calculates free mem but it matches "free"
+    # cmdline utility.
+    free -= speculative
     percent = usage_percent((total - avail), total, round_=1)
     return svmem(total, avail, percent, used, free,
                  active, inactive, wired)
diff --git a/psutil/_psutil_osx.c b/psutil/_psutil_osx.c
index 0db93fce..be08de55 100644
--- a/psutil/_psutil_osx.c
+++ b/psutil/_psutil_osx.c
@@ -711,13 +711,13 @@ psutil_virtual_mem(PyObject *self, PyObject *args) {
         return NULL;
 
     return Py_BuildValue(
-        "KKKKK",
+        "KKKKKK",
         total,
         (unsigned long long) vm.active_count * pagesize,  // active
         (unsigned long long) vm.inactive_count * pagesize,  // inactive
         (unsigned long long) vm.wire_count * pagesize,  // wired
-        // free mem; this is how vm_stat cmd does it
-        (unsigned long long) (vm.free_count - vm.speculative_count) * pagesize
+        (unsigned long long) vm.free_count * pagesize,  // free
+        (unsigned long long) vm.speculative_count * pagesize  // speculative
     );
 }
 
diff --git a/psutil/tests/test_osx.py b/psutil/tests/test_osx.py
index 557af9f9..7aabebe6 100755
--- a/psutil/tests/test_osx.py
+++ b/psutil/tests/test_osx.py
@@ -226,12 +226,6 @@ class TestSystemAPIs(unittest.TestCase):
         self.assertAlmostEqual(psutil_val, vmstat_val, delta=MEMORY_TOLERANCE)
 
     @retry_before_failing()
-    def test_vmem_available(self):
-        vmstat_val = vm_stat("inactive") + vm_stat("free")
-        psutil_val = psutil.virtual_memory().available
-        self.assertAlmostEqual(psutil_val, vmstat_val, delta=MEMORY_TOLERANCE)
-
-    @retry_before_failing()
     def test_vmem_active(self):
         vmstat_val = vm_stat("active")
         psutil_val = psutil.virtual_memory().active