bpo-34060: Report system load when running test suite for Windows

Lib/test/libregrtest/main.py

@@ -146,8 +146,8 @@ def display_progress(self, test_index, test):
         line = f"[{line}] {test}"
 
         # add the system load prefix: "load avg: 1.80 "
-        if hasattr(os, 'getloadavg'):
-            load_avg_1min = os.getloadavg()[0]
+        if self.getloadavg:
+            load_avg_1min = self.getloadavg()
             line = f"load avg: {load_avg_1min:.2f} {line}"
 
         # add the timestamp prefix:  "0:01:05 "
@@ -616,6 +616,19 @@ def _main(self, tests, kwargs):
             self.list_cases()
             sys.exit(0)
 
+        self.getloadavg = None
+        # If we're on windows and this is the parent runner (not a worker),
+        # report the load average.
+        if hasattr(os, 'getloadavg'):
+            def getloadavg_1m():
+                return os.getloadavg()[0]
+            self.getloadavg = getloadavg_1m
+        elif sys.platform == 'win32' and (self.ns.worker_args is None):
+            from test.libregrtest.win_utils import WindowsLoadTracker
+
+            load_tracker = WindowsLoadTracker()
+            self.getloadavg = load_tracker.getloadavg
+
         self.run_tests()
         self.display_result()
 

Lib/test/libregrtest/win_utils.py

@@ -0,0 +1,100 @@
+import subprocess
+import sys
+import os
+import _winapi
+import msvcrt
+import uuid
+from test import support
+
+
+# Max size of asynchronous reads
+BUFSIZE = 8192
+# Exponential damping factor (see below)
+LOAD_FACTOR_1 = 0.9200444146293232478931553241
+# Seconds per measurement
+SAMPLING_INTERVAL = 5
+COUNTER_NAME = r'\System\Processor Queue Length'
+
+
+class WindowsLoadTracker():
+    """
+    This class asynchronously interacts with the `typeperf` command to read
+    the system load on Windows. Mulitprocessing and threads can't be used
+    here because they interfere with the test suite's cases for those
+    modules.
+    """
+
+    def __init__(self):
+        self.load = 0.0
+        self.start()
+
+    def start(self):
+        # Create a named pipe which allows for asynchronous IO in Windows
+        pipe_name =  r'\\.\pipe\typeperf_output_' + str(uuid.uuid4())
+
+        open_mode =  _winapi.PIPE_ACCESS_INBOUND
+        open_mode |= _winapi.FILE_FLAG_FIRST_PIPE_INSTANCE
+        open_mode |= _winapi.FILE_FLAG_OVERLAPPED
+
+        # This is the read end of the pipe, where we will be grabbing output
+        self.pipe = _winapi.CreateNamedPipe(
+            pipe_name, open_mode, _winapi.PIPE_WAIT,
+            1, BUFSIZE, BUFSIZE, _winapi.NMPWAIT_WAIT_FOREVER, _winapi.NULL
+        )
+        # The write end of the pipe which is passed to the created process
+        pipe_write_end = _winapi.CreateFile(
+            pipe_name, _winapi.GENERIC_WRITE, 0, _winapi.NULL,
+            _winapi.OPEN_EXISTING, 0, _winapi.NULL
+        )
+        # Open up the handle as a python file object so we can pass it to
+        # subprocess
+        command_stdout = msvcrt.open_osfhandle(pipe_write_end, 0)
+
+        # Connect to the read end of the pipe in overlap/async mode
+        overlap = _winapi.ConnectNamedPipe(self.pipe, overlapped=True)
+        overlap.GetOverlappedResult(True)
+
+        # Spawn off the load monitor
+        command = ['typeperf', COUNTER_NAME, '-si', str(SAMPLING_INTERVAL)]
+        self.p = subprocess.Popen(command, stdout=command_stdout, cwd=support.SAVEDCWD)
+
+        # Close our copy of the write end of the pipe
+        os.close(command_stdout)
+
+    def __del__(self):
+        self.p.kill()
+        self.p.wait()
+
+    def read_output(self):
+        import _winapi
+
+        overlapped, _ = _winapi.ReadFile(self.pipe, BUFSIZE, True)
+        bytes_read, res = overlapped.GetOverlappedResult(False)
+        if res != 0:
+            return
+
+        return overlapped.getbuffer().decode()
+
+    def getloadavg(self):
+        typeperf_output = self.read_output()
+        # Nothing to update, just return the current load
+        if not typeperf_output:
+            return self.load
+
+        # Process the backlog of load values
+        for line in typeperf_output.splitlines():
+            # typeperf outputs in a CSV format like this:
+            # "07/19/2018 01:32:26.605","3.000000"
+            toks = line.split(',')
+            # Ignore blank lines and the initial header
+            if line.strip() == '' or (COUNTER_NAME in line) or len(toks) != 2:
+                continue
+
+            load = float(toks[1].replace('"', ''))
+            # We use an exponentially weighted moving average, imitating the
+            # load calculation on Unix systems.
+            # https://en.wikipedia.org/wiki/Load_(computing)#Unix-style_load_calculation
+            new_load = self.load * LOAD_FACTOR_1 + load * (1.0 - LOAD_FACTOR_1)
+            self.load = new_load
+
+        return self.load

Misc/NEWS.d/next/Windows/2018-07-20-13-09-19.bpo-34060.v-z87j.rst

@@ -0,0 +1,2 @@
+Report system load when running test suite on Windows. Patch by Ammar Askar.
+Based on prior work by Jeremy Kloth.