diff --git a/hgext/largefiles/lfutil.py b/hgext/largefiles/lfutil.py
--- a/hgext/largefiles/lfutil.py
+++ b/hgext/largefiles/lfutil.py
@@ -84,7 +84,7 @@
         home = encoding.environ.get('HOME')
         if home:
             return os.path.join(home, 'Library', 'Caches', longname)
-    elif pycompat.osname == 'posix':
+    elif pycompat.isposix:
         path = encoding.environ.get('XDG_CACHE_HOME')
         if path:
             return os.path.join(path, longname)
diff --git a/mercurial/util.py b/mercurial/util.py
--- a/mercurial/util.py
+++ b/mercurial/util.py
@@ -313,7 +313,7 @@
             return memoryview(sliceable)[offset:offset + length]
         return memoryview(sliceable)[offset:]
 
-closefds = pycompat.osname == 'posix'
+closefds = pycompat.isposix
 
 _chunksize = 4096
 
diff --git a/mercurial/worker.py b/mercurial/worker.py
--- a/mercurial/worker.py
+++ b/mercurial/worker.py
@@ -53,7 +53,7 @@
             raise error.Abort(_('number of cpus must be an integer'))
     return min(max(countcpus(), 4), 32)
 
-if pycompat.osname == 'posix':
+if pycompat.isposix:
     _startupcost = 0.01
 else:
     _startupcost = 1e30