Use psutil.cpu_count(logical=False) in auto_detect_cpus()

changelog/553.bugfix.rst

@@ -0,0 +1 @@
+When using ``-n auto``, count the number of physical CPU cores instead of logical ones.

setup.py

@@ -1,6 +1,12 @@
 from setuptools import setup, find_packages
 
-install_requires = ["execnet>=1.1", "pytest>=4.4.0", "pytest-forked", "six"]
+install_requires = [
+    "execnet>=1.1",
+    "psutil>=3.0.0",
+    "pytest>=4.4.0",
+    "pytest-forked",
+    "six",
+]
 
 
 with open("README.rst") as f:

src/xdist/plugin.py

@@ -1,31 +1,12 @@
-import os
 import uuid
 
+import psutil
 import py
 import pytest
 
 
 def auto_detect_cpus():
-    try:
-        from os import sched_getaffinity
-    except ImportError:
-        if os.environ.get("TRAVIS") == "true":
-            # workaround https://bitbucket.org/pypy/pypy/issues/2375
-            return 2
-        try:
-            from os import cpu_count
-        except ImportError:
-            from multiprocessing import cpu_count
-    else:
-
-        def cpu_count():
-            return len(sched_getaffinity(0))
-
-    try:
-        n = cpu_count()
-    except NotImplementedError:
-        return 1
-    return n if n else 1
+    return psutil.cpu_count(logical=False) or psutil.cpu_count() or 1
 
 
 class AutoInt(int):

testing/test_plugin.py

@@ -35,17 +35,10 @@ def test_dist_options(testdir):
 
 
 def test_auto_detect_cpus(testdir, monkeypatch):
-    import os
+    import psutil
     from xdist.plugin import pytest_cmdline_main as check_options
 
-    if hasattr(os, "sched_getaffinity"):
-        monkeypatch.setattr(os, "sched_getaffinity", lambda _pid: set(range(99)))
-    elif hasattr(os, "cpu_count"):
-        monkeypatch.setattr(os, "cpu_count", lambda: 99)
-    else:
-        import multiprocessing
-
-        monkeypatch.setattr(multiprocessing, "cpu_count", lambda: 99)
+    monkeypatch.setattr(psutil, "cpu_count", lambda logical=True: 99)
 
     config = testdir.parseconfigure("-n2")
     assert config.getoption("numprocesses") == 2
@@ -58,10 +51,9 @@ def test_auto_detect_cpus(testdir, monkeypatch):
     assert config.getoption("usepdb")
     assert config.getoption("numprocesses") == 0
 
-    monkeypatch.delattr(os, "sched_getaffinity", raising=False)
-    monkeypatch.setenv("TRAVIS", "true")
+    monkeypatch.setattr(psutil, "cpu_count", lambda logical=True: None)
     config = testdir.parseconfigure("-nauto")
-    assert config.getoption("numprocesses") == 2
+    assert config.getoption("numprocesses") == 1
 
 
 def test_boxed_with_collect_only(testdir):