# ===----------------------------------------------------------------------===##
#
# Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
# See https://llvm.org/LICENSE.txt for license information.
# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
#
# ===----------------------------------------------------------------------===##
import re
import select
import socket
import subprocess
import tempfile
import threading
from typing import List
def _get_cpu_count() -> int:
# Determine the number of cores by listing a /sys directory. Older devices
# lack `nproc`. Even if a static toybox binary is pushed to the device, it may
# return an incorrect value. (e.g. On a Nexus 7 running Android 5.0, toybox
# nproc returns 1 even though the device has 4 CPUs.)
job = subprocess.run(["adb", "shell", "ls /sys/devices/system/cpu"],
encoding="utf8", check=False,
stdout=subprocess.PIPE, stderr=subprocess.PIPE)
if job.returncode == 1:
# Maybe adb is missing, maybe ANDROID_SERIAL needs to be defined, maybe the
# /sys subdir isn't there. Most errors will be handled later, just use one
# job. (N.B. The adb command still succeeds even if ls fails on older
# devices that lack the shell_v2 adb feature.)
return 1
# Make sure there are no CR characters in the output. Pre-shell_v2, the adb
# stdout comes from a master pty so newlines are CRLF-delimited. On Windows,
# LF might also get expanded to CRLF.
cpu_listing = job.stdout.replace('\r', '\n')
# Count lines that match "cpu${DIGITS}".
result = len([line for line in cpu_listing.splitlines()
if re.match(r'cpu(\d)+$', line)])
# Restrict the result to something reasonable.
if result < 1:
result = 1
if result > 1024:
result = 1024
return result
def _job_limit_socket_thread(temp_dir: tempfile.TemporaryDirectory,
server: socket.socket, job_count: int) -> None:
"""Service the job limit server socket, accepting only as many connections
as there should be concurrent jobs.
"""
clients: List[socket.socket] = []
while True:
rlist = list(clients)
if len(clients) < job_count:
rlist.append(server)
rlist, _, _ = select.select(rlist, [], [])
for sock in rlist:
if sock == server:
new_client, _ = server.accept()
new_client.send(b"x")
clients.append(new_client)
else:
sock.close()
clients.remove(sock)
def adb_job_limit_socket() -> str:
"""An Android device can frequently have many fewer cores than the host
(e.g. 4 versus 128). We want to exploit all the device cores without
overburdening it.
Create a Unix domain socket that only allows as many connections as CPUs on
the Android device.
"""
# Create the job limit server socket.
temp_dir = tempfile.TemporaryDirectory(prefix="libcxx_")
sock_addr = temp_dir.name + "/adb_job.sock"
server = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
server.bind(sock_addr)
server.listen(1)
# Spawn a thread to service the socket. As a daemon thread, its existence
# won't prevent interpreter shutdown. The temp dir will still be removed on
# shutdown.
cpu_count = _get_cpu_count()
threading.Thread(target=_job_limit_socket_thread,
args=(temp_dir, server, cpu_count),
daemon=True).start()
return sock_addr
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