Current File : //snap/core20/2379/lib/python3.8/test/libregrtest/win_utils.py
import _winapi
import math
import msvcrt
import os
import subprocess
import uuid
import winreg
from test import support
from test.libregrtest.utils import print_warning
# Max size of asynchronous reads
BUFSIZE = 8192
# Seconds per measurement
SAMPLING_INTERVAL = 1
# Exponential damping factor to compute exponentially weighted moving average
# on 1 minute (60 seconds)
LOAD_FACTOR_1 = 1 / math.exp(SAMPLING_INTERVAL / 60)
# Initialize the load using the arithmetic mean of the first NVALUE values
# of the Processor Queue Length
NVALUE = 5
# Windows registry subkey of HKEY_LOCAL_MACHINE where the counter names
# of typeperf are registered
COUNTER_REGISTRY_KEY = (r"SOFTWARE\Microsoft\Windows NT\CurrentVersion"
r"\Perflib\CurrentLanguage")
class WindowsLoadTracker():
"""
This class asynchronously interacts with the `typeperf` command to read
the system load on Windows. Multiprocessing and threads can't be used
here because they interfere with the test suite's cases for those
modules.
"""
def __init__(self):
self._values = []
self._load = None
self._buffer = ''
self._popen = None
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
counter_name = self._get_counter_name()
command = ['typeperf', counter_name, '-si', str(SAMPLING_INTERVAL)]
self._popen = subprocess.Popen(' '.join(command), stdout=command_stdout, cwd=support.SAVEDCWD)
# Close our copy of the write end of the pipe
os.close(command_stdout)
def _get_counter_name(self):
# accessing the registry to get the counter localization name
with winreg.OpenKey(winreg.HKEY_LOCAL_MACHINE, COUNTER_REGISTRY_KEY) as perfkey:
counters = winreg.QueryValueEx(perfkey, 'Counter')[0]
# Convert [key1, value1, key2, value2, ...] list
# to {key1: value1, key2: value2, ...} dict
counters = iter(counters)
counters_dict = dict(zip(counters, counters))
# System counter has key '2' and Processor Queue Length has key '44'
system = counters_dict['2']
process_queue_length = counters_dict['44']
return f'"\\{system}\\{process_queue_length}"'
def close(self, kill=True):
if self._popen is None:
return
self._load = None
if kill:
self._popen.kill()
self._popen.wait()
self._popen = None
def __del__(self):
self.close()
def _parse_line(self, line):
# typeperf outputs in a CSV format like this:
# "07/19/2018 01:32:26.605","3.000000"
# (date, process queue length)
tokens = line.split(',')
if len(tokens) != 2:
raise ValueError
value = tokens[1]
if not value.startswith('"') or not value.endswith('"'):
raise ValueError
value = value[1:-1]
return float(value)
def _read_lines(self):
overlapped, _ = _winapi.ReadFile(self.pipe, BUFSIZE, True)
bytes_read, res = overlapped.GetOverlappedResult(False)
if res != 0:
return ()
output = overlapped.getbuffer()
output = output.decode('oem', 'replace')
output = self._buffer + output
lines = output.splitlines(True)
# bpo-36670: typeperf only writes a newline *before* writing a value,
# not after. Sometimes, the written line in incomplete (ex: only
# timestamp, without the process queue length). Only pass the last line
# to the parser if it's a valid value, otherwise store it in
# self._buffer.
try:
self._parse_line(lines[-1])
except ValueError:
self._buffer = lines.pop(-1)
else:
self._buffer = ''
return lines
def getloadavg(self):
if self._popen is None:
return None
returncode = self._popen.poll()
if returncode is not None:
self.close(kill=False)
return None
try:
lines = self._read_lines()
except BrokenPipeError:
self.close()
return None
for line in lines:
line = line.rstrip()
# Ignore the initial header:
# "(PDH-CSV 4.0)","\\\\WIN\\System\\Processor Queue Length"
if 'PDH-CSV' in line:
continue
# Ignore blank lines
if not line:
continue
try:
processor_queue_length = self._parse_line(line)
except ValueError:
print_warning("Failed to parse typeperf output: %a" % line)
continue
# 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
# https://en.wikipedia.org/wiki/Moving_average#Exponential_moving_average
if self._load is not None:
self._load = (self._load * LOAD_FACTOR_1
+ processor_queue_length * (1.0 - LOAD_FACTOR_1))
elif len(self._values) < NVALUE:
self._values.append(processor_queue_length)
else:
self._load = sum(self._values) / len(self._values)
return self._load
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