#1083 / #1084: implement linux-specific ppid_map() function speending…

… things up from 2x to 2.4x

HISTORY.rst

@@ -10,7 +10,7 @@
 - 1173_: introduced PSUTIL_DEBUG environment variable which can be set in order
   to print useful debug messages on stderr (useful in case of nasty errors).
 - 1177_: added support for sensors_battery() on OSX.  (patch by Arnon Yaari)
-- 1183_: Process.children() is around 2.2x faster on UNIX.
+- 1183_: Process.children() is 2x faster on UNIX and 2.4x faster on Linux.
 
 **Bug fixes**
 

psutil/__init__.py

@@ -255,11 +255,11 @@
 
 
 if hasattr(_psplatform, 'ppid_map'):
-    # Windows only (C).
+    # Faster version (Windows and Linux).
     _ppid_map = _psplatform.ppid_map
 else:
     def _ppid_map():
-        """Obtain a {pid: ppid, ...} dict for all running processes in
+        """Return a {pid: ppid, ...} dict for all running processes in
         one shot. Used to speed up Process.children().
         """
         ret = {}

psutil/_pslinux.py

@@ -1356,6 +1356,27 @@ def pid_exists(pid):
             return pid in pids()
 
 
+def ppid_map():
+    """Obtain a {pid: ppid, ...} dict for all running processes in
+    one shot. Used to speed up Process.children().
+    """
+    ret = {}
+    procfs_path = get_procfs_path()
+    for pid in pids():
+        try:
+            with open_binary("%s/%s/stat" % (procfs_path, pid)) as f:
+                data = f.read()
+        except EnvironmentError as err:
+            if err.errno not in (errno.ENOENT, errno.EPERM, errno.EACCES):
+                raise
+        else:
+            rpar = data.rfind(b')')
+            dset = data[rpar + 2:].split()
+            ppid = int(dset[1])
+            ret[pid] = ppid
+    return ret
+
+
 def wrap_exceptions(fun):
     """Decorator which translates bare OSError and IOError exceptions
     into NoSuchProcess and AccessDenied.