368 lines
14 KiB
Python
368 lines
14 KiB
Python
###############################################################################
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# Basic context management with LokyContext and provides
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# compat for UNIX 2.7 and 3.3
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#
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# author: Thomas Moreau and Olivier Grisel
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#
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# adapted from multiprocessing/context.py
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# * Create a context ensuring loky uses only objects that are compatible
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# * Add LokyContext to the list of context of multiprocessing so loky can be
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# used with multiprocessing.set_start_method
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# * Add some compat function for python2.7 and 3.3.
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#
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from __future__ import division
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import os
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import sys
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import subprocess
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import traceback
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import warnings
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import multiprocessing as mp
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from .process import LokyProcess, LokyInitMainProcess
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START_METHODS = ['loky', 'loky_init_main']
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_DEFAULT_START_METHOD = None
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# Cache for the number of physical cores to avoid repeating subprocess calls.
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# It should not change during the lifetime of the program.
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physical_cores_cache = None
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if sys.version_info[:2] >= (3, 4):
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from multiprocessing import get_context as mp_get_context
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from multiprocessing.context import assert_spawning, set_spawning_popen
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from multiprocessing.context import get_spawning_popen, BaseContext
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START_METHODS += ['spawn']
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if sys.platform != 'win32':
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START_METHODS += ['fork', 'forkserver']
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def get_context(method=None):
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# Try to overload the default context
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method = method or _DEFAULT_START_METHOD or "loky"
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if method == "fork":
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# If 'fork' is explicitly requested, warn user about potential
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# issues.
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warnings.warn("`fork` start method should not be used with "
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"`loky` as it does not respect POSIX. Try using "
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"`spawn` or `loky` instead.", UserWarning)
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try:
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context = mp_get_context(method)
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except ValueError:
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raise ValueError("Unknown context '{}'. Value should be in {}."
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.format(method, START_METHODS))
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return context
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else:
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if sys.platform != 'win32':
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import threading
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# Mechanism to check that the current thread is spawning a process
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_tls = threading.local()
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popen_attr = 'spawning_popen'
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else:
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from multiprocessing.forking import Popen
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_tls = Popen._tls
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popen_attr = 'process_handle'
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BaseContext = object
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def get_spawning_popen():
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return getattr(_tls, popen_attr, None)
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def set_spawning_popen(popen):
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setattr(_tls, popen_attr, popen)
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def assert_spawning(obj):
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if get_spawning_popen() is None:
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raise RuntimeError(
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'%s objects should only be shared between processes'
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' through inheritance' % type(obj).__name__
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)
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def get_context(method=None):
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method = method or _DEFAULT_START_METHOD or 'loky'
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if method == "loky":
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return LokyContext()
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elif method == "loky_init_main":
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return LokyInitMainContext()
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else:
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raise ValueError("Unknown context '{}'. Value should be in {}."
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.format(method, START_METHODS))
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def set_start_method(method, force=False):
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global _DEFAULT_START_METHOD
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if _DEFAULT_START_METHOD is not None and not force:
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raise RuntimeError('context has already been set')
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assert method is None or method in START_METHODS, (
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"'{}' is not a valid start_method. It should be in {}"
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.format(method, START_METHODS))
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_DEFAULT_START_METHOD = method
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def get_start_method():
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return _DEFAULT_START_METHOD
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def cpu_count(only_physical_cores=False):
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"""Return the number of CPUs the current process can use.
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The returned number of CPUs accounts for:
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* the number of CPUs in the system, as given by
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``multiprocessing.cpu_count``;
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* the CPU affinity settings of the current process
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(available with Python 3.4+ on some Unix systems);
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* CFS scheduler CPU bandwidth limit (available on Linux only, typically
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set by docker and similar container orchestration systems);
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* the value of the LOKY_MAX_CPU_COUNT environment variable if defined.
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and is given as the minimum of these constraints.
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If ``only_physical_cores`` is True, return the number of physical cores
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instead of the number of logical cores (hyperthreading / SMT). Note that
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this option is not enforced if the number of usable cores is controlled in
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any other way such as: process affinity, restricting CFS scheduler policy
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or the LOKY_MAX_CPU_COUNT environment variable. If the number of physical
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cores is not found, return the number of logical cores.
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It is also always larger or equal to 1.
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"""
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# TODO: use os.cpu_count when dropping python 2 support
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try:
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cpu_count_mp = mp.cpu_count()
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except NotImplementedError:
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cpu_count_mp = 1
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cpu_count_user = _cpu_count_user(cpu_count_mp)
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aggregate_cpu_count = min(cpu_count_mp, cpu_count_user)
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if only_physical_cores:
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cpu_count_physical, exception = _count_physical_cores()
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if cpu_count_user < cpu_count_mp:
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# Respect user setting
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cpu_count = max(cpu_count_user, 1)
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elif cpu_count_physical == "not found":
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# Fallback to default behavior
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if exception is not None:
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# warns only the first time
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warnings.warn(
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"Could not find the number of physical cores for the "
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"following reason:\n" + str(exception) + "\n"
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"Returning the number of logical cores instead. You can "
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"silence this warning by setting LOKY_MAX_CPU_COUNT to "
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"the number of cores you want to use.")
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if sys.version_info >= (3, 5):
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# TODO remove the version check when dropping py2 support
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traceback.print_tb(exception.__traceback__)
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cpu_count = max(aggregate_cpu_count, 1)
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else:
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return cpu_count_physical
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else:
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cpu_count = max(aggregate_cpu_count, 1)
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return cpu_count
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def _cpu_count_user(cpu_count_mp):
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"""Number of user defined available CPUs"""
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import math
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# Number of available CPUs given affinity settings
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cpu_count_affinity = cpu_count_mp
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if hasattr(os, 'sched_getaffinity'):
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try:
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cpu_count_affinity = len(os.sched_getaffinity(0))
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except NotImplementedError:
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pass
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# CFS scheduler CPU bandwidth limit
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# available in Linux since 2.6 kernel
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cpu_count_cfs = cpu_count_mp
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cfs_quota_fname = "/sys/fs/cgroup/cpu/cpu.cfs_quota_us"
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cfs_period_fname = "/sys/fs/cgroup/cpu/cpu.cfs_period_us"
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if os.path.exists(cfs_quota_fname) and os.path.exists(cfs_period_fname):
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with open(cfs_quota_fname, 'r') as fh:
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cfs_quota_us = int(fh.read())
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with open(cfs_period_fname, 'r') as fh:
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cfs_period_us = int(fh.read())
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if cfs_quota_us > 0 and cfs_period_us > 0:
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# Make sure this quantity is an int as math.ceil returns a
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# float in python2.7. (See issue #165)
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cpu_count_cfs = int(math.ceil(cfs_quota_us / cfs_period_us))
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# User defined soft-limit passed as a loky specific environment variable.
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cpu_count_loky = int(os.environ.get('LOKY_MAX_CPU_COUNT', cpu_count_mp))
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return min(cpu_count_affinity, cpu_count_cfs, cpu_count_loky)
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def _count_physical_cores():
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"""Return a tuple (number of physical cores, exception)
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If the number of physical cores is found, exception is set to None.
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If it has not been found, return ("not found", exception).
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The number of physical cores is cached to avoid repeating subprocess calls.
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"""
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exception = None
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# First check if the value is cached
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global physical_cores_cache
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if physical_cores_cache is not None:
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return physical_cores_cache, exception
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# Not cached yet, find it
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try:
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if sys.platform == "linux":
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cpu_info = subprocess.run(
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"lscpu --parse=core".split(" "), capture_output=True)
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cpu_info = cpu_info.stdout.decode("utf-8").splitlines()
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cpu_info = {line for line in cpu_info if not line.startswith("#")}
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cpu_count_physical = len(cpu_info)
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elif sys.platform == "win32":
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cpu_info = subprocess.run(
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"wmic CPU Get NumberOfCores /Format:csv".split(" "),
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capture_output=True)
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cpu_info = cpu_info.stdout.decode('utf-8').splitlines()
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cpu_info = [l.split(",")[1] for l in cpu_info
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if (l and l != "Node,NumberOfCores")]
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cpu_count_physical = sum(map(int, cpu_info))
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elif sys.platform == "darwin":
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cpu_info = subprocess.run(
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"sysctl -n hw.physicalcpu".split(" "), capture_output=True)
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cpu_info = cpu_info.stdout.decode('utf-8')
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cpu_count_physical = int(cpu_info)
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else:
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raise NotImplementedError(
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"unsupported platform: {}".format(sys.platform))
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# if cpu_count_physical < 1, we did not find a valid value
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if cpu_count_physical < 1:
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raise ValueError(
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"found {} physical cores < 1".format(cpu_count_physical))
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except Exception as e:
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exception = e
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cpu_count_physical = "not found"
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# Put the result in cache
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physical_cores_cache = cpu_count_physical
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return cpu_count_physical, exception
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class LokyContext(BaseContext):
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"""Context relying on the LokyProcess."""
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_name = 'loky'
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Process = LokyProcess
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cpu_count = staticmethod(cpu_count)
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def Queue(self, maxsize=0, reducers=None):
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'''Returns a queue object'''
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from .queues import Queue
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return Queue(maxsize, reducers=reducers,
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ctx=self.get_context())
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def SimpleQueue(self, reducers=None):
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'''Returns a queue object'''
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from .queues import SimpleQueue
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return SimpleQueue(reducers=reducers, ctx=self.get_context())
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if sys.version_info[:2] < (3, 4):
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"""Compat for python2.7/3.3 for necessary methods in Context"""
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def get_context(self):
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return self
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def get_start_method(self):
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return self._name
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def Pipe(self, duplex=True):
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'''Returns two connection object connected by a pipe'''
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return mp.Pipe(duplex)
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if sys.platform != "win32":
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"""Use the compat Manager for python2.7/3.3 on UNIX to avoid
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relying on fork processes
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"""
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def Manager(self):
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"""Returns a manager object"""
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from .managers import LokyManager
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m = LokyManager()
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m.start()
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return m
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else:
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"""Compat for context on Windows and python2.7/3.3. Using regular
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multiprocessing objects as it does not rely on fork.
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"""
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from multiprocessing import synchronize
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Semaphore = staticmethod(synchronize.Semaphore)
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BoundedSemaphore = staticmethod(synchronize.BoundedSemaphore)
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Lock = staticmethod(synchronize.Lock)
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RLock = staticmethod(synchronize.RLock)
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Condition = staticmethod(synchronize.Condition)
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Event = staticmethod(synchronize.Event)
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Manager = staticmethod(mp.Manager)
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if sys.platform != "win32":
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"""For Unix platform, use our custom implementation of synchronize
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relying on ctypes to interface with pthread semaphores.
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"""
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def Semaphore(self, value=1):
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"""Returns a semaphore object"""
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from .synchronize import Semaphore
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return Semaphore(value=value)
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def BoundedSemaphore(self, value):
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"""Returns a bounded semaphore object"""
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from .synchronize import BoundedSemaphore
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return BoundedSemaphore(value)
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def Lock(self):
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"""Returns a lock object"""
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from .synchronize import Lock
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return Lock()
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def RLock(self):
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"""Returns a recurrent lock object"""
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from .synchronize import RLock
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return RLock()
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def Condition(self, lock=None):
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"""Returns a condition object"""
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from .synchronize import Condition
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return Condition(lock)
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def Event(self):
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"""Returns an event object"""
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from .synchronize import Event
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return Event()
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class LokyInitMainContext(LokyContext):
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"""Extra context with LokyProcess, which does load the main module
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This context is used for compatibility in the case ``cloudpickle`` is not
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present on the running system. This permits to load functions defined in
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the ``main`` module, using proper safeguards. The declaration of the
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``executor`` should be protected by ``if __name__ == "__main__":`` and the
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functions and variable used from main should be out of this block.
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This mimics the default behavior of multiprocessing under Windows and the
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behavior of the ``spawn`` start method on a posix system for python3.4+.
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For more details, see the end of the following section of python doc
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https://docs.python.org/3/library/multiprocessing.html#multiprocessing-programming
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"""
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_name = 'loky_init_main'
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Process = LokyInitMainProcess
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if sys.version_info > (3, 4):
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"""Register loky context so it works with multiprocessing.get_context"""
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ctx_loky = LokyContext()
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mp.context._concrete_contexts['loky'] = ctx_loky
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mp.context._concrete_contexts['loky_init_main'] = LokyInitMainContext()
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