cborutil: change buffering strategy
Profiling revealed that we were spending a lot of time on the
line that was concatenating the old buffer with the incoming data
when attempting to decode long byte strings, such as manifest
revisions.
Essentially, we were feeding N chunks of size len(X) << len(Y) into
decode() and continuously allocating a new, larger buffer to hold
the undecoded input. This created substantial memory churn and
slowed down execution.
Changing the code to aggregate pending chunks in a list until we
have enough data to fully decode the next atom makes things much
more efficient.
I don't have exact data, but I recall the old code spending >1s
on manifest fulltexts from the mozilla-unified repo. The new code
doesn't significantly appear in profile output.
Differential Revision: https://phab.mercurial-scm.org/D4854
# A minimal client for Mercurial's command server
from __future__ import absolute_import, print_function
import os
import signal
import socket
import struct
import subprocess
import sys
import time
try:
import cStringIO as io
stringio = io.StringIO
except ImportError:
import io
stringio = io.StringIO
def connectpipe(path=None):
cmdline = ['hg', 'serve', '--cmdserver', 'pipe']
if path:
cmdline += ['-R', path]
server = subprocess.Popen(cmdline, stdin=subprocess.PIPE,
stdout=subprocess.PIPE)
return server
class unixconnection(object):
def __init__(self, sockpath):
self.sock = sock = socket.socket(socket.AF_UNIX)
sock.connect(sockpath)
self.stdin = sock.makefile('wb')
self.stdout = sock.makefile('rb')
def wait(self):
self.stdin.close()
self.stdout.close()
self.sock.close()
class unixserver(object):
def __init__(self, sockpath, logpath=None, repopath=None):
self.sockpath = sockpath
cmdline = ['hg', 'serve', '--cmdserver', 'unix', '-a', sockpath]
if repopath:
cmdline += ['-R', repopath]
if logpath:
stdout = open(logpath, 'a')
stderr = subprocess.STDOUT
else:
stdout = stderr = None
self.server = subprocess.Popen(cmdline, stdout=stdout, stderr=stderr)
# wait for listen()
while self.server.poll() is None:
if os.path.exists(sockpath):
break
time.sleep(0.1)
def connect(self):
return unixconnection(self.sockpath)
def shutdown(self):
os.kill(self.server.pid, signal.SIGTERM)
self.server.wait()
def writeblock(server, data):
server.stdin.write(struct.pack('>I', len(data)))
server.stdin.write(data)
server.stdin.flush()
def readchannel(server):
data = server.stdout.read(5)
if not data:
raise EOFError
channel, length = struct.unpack('>cI', data)
if channel in 'IL':
return channel, length
else:
return channel, server.stdout.read(length)
def sep(text):
return text.replace('\\', '/')
def runcommand(server, args, output=sys.stdout, error=sys.stderr, input=None,
outfilter=lambda x: x):
print('*** runcommand', ' '.join(args))
sys.stdout.flush()
server.stdin.write('runcommand\n')
writeblock(server, '\0'.join(args))
if not input:
input = stringio()
while True:
ch, data = readchannel(server)
if ch == 'o':
output.write(outfilter(data))
output.flush()
elif ch == 'e':
error.write(data)
error.flush()
elif ch == 'I':
writeblock(server, input.read(data))
elif ch == 'L':
writeblock(server, input.readline(data))
elif ch == 'r':
ret, = struct.unpack('>i', data)
if ret != 0:
print(' [%d]' % ret)
return ret
else:
print("unexpected channel %c: %r" % (ch, data))
if ch.isupper():
return
def check(func, connect=connectpipe):
sys.stdout.flush()
server = connect()
try:
return func(server)
finally:
server.stdin.close()
server.wait()