bundle2: increase payload part chunk size to 32kb
Bundle2 payload parts are framed chunks. Esentially, we obtain
data in equal size chunks of size `preferedchunksize` and emit those
to a generator. That generator is fed into a compressor (which can
be the no-op compressor, which just re-emits the generator). And
the output from the compressor likely goes to a file descriptor
or socket.
What this means is that small chunk sizes create more Python objects
and Python function calls than larger chunk sizes. And as we know,
Python object and function call overhead in performance sensitive
code matters (at least with CPython).
This commit increases the bundle2 part payload chunk size from 4k
to 32k. Practically speaking, this means that the chunks we feed
into a compressor (implemented in C code) or feed directly into a
file handle or socket write() are larger. It's possible the chunks
might be larger than what the receiver can handle in one logical
operation. But at that point, we're in C code, which is much more
efficient at dealing with splitting up the chunk and making multiple
function calls than Python is.
A downside to larger chunks is that the receiver has to wait for that
much data to arrive (either raw or from a decompressor) before it
can process the chunk. But 32kb still feels like a small buffer to
have to wait for. And in many cases, the client will convert from
8 read(4096) to 1 read(32768). That's happening in Python land. So
we cut down on the number of Python objects and function calls,
making the client faster as well. I don't think there are any
significant concerns to increasing the payload chunk size to 32kb.
The impact of this change on performance significant. Using `curl`
to obtain a stream clone bundle2 payload from a server on localhost
serving the mozilla-unified repository:
before: 20.78 user; 7.71 system; 80.5 MB/s
after: 13.90 user; 3.51 system; 132 MB/s
legacy: 9.72 user; 8.16 system; 132 MB/s
bundle2 stream clone generation is still more resource intensive than
legacy stream clone (that's likely because of the use of a
util.chunkbuffer). But the throughput is the same. We might
be in territory we're this is effectively a benchmark of the
networking stack or Python's syscall throughput.
From the client perspective, `hg clone -U --stream`:
before: 33.50 user; 7.95 system; 53.3 MB/s
after: 22.82 user; 7.33 system; 72.7 MB/s
legacy: 29.96 user; 7.94 system; 58.0 MB/s
And for `hg clone --stream` with a working directory update of
~230k files:
after: 119.55 user; 26.47 system; 0:57.08 wall
legacy: 126.98 user; 26.94 system; 1:05.56 wall
So, it appears that bundle2's stream clone is now definitively faster
than legacy stream clone!
Differential Revision: https://phab.mercurial-scm.org/D1932
"""This unit test primarily tests parsers.parse_index2().
It also checks certain aspects of the parsers module as a whole.
"""
from __future__ import absolute_import, print_function
import struct
import subprocess
import sys
from mercurial.node import (
nullid,
nullrev,
)
from mercurial import (
policy,
)
parsers = policy.importmod(r'parsers')
# original python implementation
def gettype(q):
return int(q & 0xFFFF)
def offset_type(offset, type):
return long(long(offset) << 16 | type)
indexformatng = ">Qiiiiii20s12x"
def py_parseindex(data, inline) :
s = 64
cache = None
index = []
nodemap = {nullid: nullrev}
n = off = 0
l = len(data) - s
append = index.append
if inline:
cache = (0, data)
while off <= l:
e = struct.unpack(indexformatng, data[off:off + s])
nodemap[e[7]] = n
append(e)
n += 1
if e[1] < 0:
break
off += e[1] + s
else:
while off <= l:
e = struct.unpack(indexformatng, data[off:off + s])
nodemap[e[7]] = n
append(e)
n += 1
off += s
e = list(index[0])
type = gettype(e[0])
e[0] = offset_type(0, type)
index[0] = tuple(e)
# add the magic null revision at -1
index.append((0, 0, 0, -1, -1, -1, -1, nullid))
return index, cache
data_inlined = '\x00\x01\x00\x01\x00\x00\x00\x00\x00\x00\x01\x8c' \
'\x00\x00\x04\x07\x00\x00\x00\x00\x00\x00\x15\x15\xff\xff\xff' \
'\xff\xff\xff\xff\xff\xebG\x97\xb7\x1fB\x04\xcf\x13V\x81\tw\x1b' \
'w\xdduR\xda\xc6\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00' \
'x\x9c\x9d\x93?O\xc30\x10\xc5\xf7|\x8a\xdb\x9a\xa8m\x06\xd8*\x95' \
'\x81B\xa1\xa2\xa2R\xcb\x86Pd\x9a\x0b5$vd_\x04\xfd\xf6\x9c\xff@' \
'\x11!\x0b\xd9\xec\xf7\xbbw\xe7gG6\xad6\x04\xdaN\xc0\x92\xa0$)' \
'\xb1\x82\xa2\xd1%\x16\xa4\x8b7\xa9\xca\xd4-\xb2Y\x02\xfc\xc9' \
'\xcaS\xf9\xaeX\xed\xb6\xd77Q\x02\x83\xd4\x19\xf5--Y\xea\xe1W' \
'\xab\xed\x10\xceR\x0f_\xdf\xdf\r\xe1,\xf5\xf0\xcb\xf5 \xceR\x0f' \
'_\xdc\x0e\x0e\xc3R\x0f_\xae\x96\x9b!\x9e\xa5\x1e\xbf\xdb,\x06' \
'\xc7q\x9a/\x88\x82\xc3B\xea\xb5\xb4TJ\x93\xb6\x82\x0e\xe16\xe6' \
'KQ\xdb\xaf\xecG\xa3\xd1 \x01\xd3\x0b_^\xe8\xaa\xa0\xae\xad\xd1' \
'&\xbef\x1bz\x08\xb0|\xc9Xz\x06\xf6Z\x91\x90J\xaa\x17\x90\xaa' \
'\xd2\xa6\x11$5C\xcf\xba#\xa0\x03\x02*2\x92-\xfc\xb1\x94\xdf\xe2' \
'\xae\xb8\'m\x8ey0^\x85\xd3\x82\xb4\xf0`:\x9c\x00\x8a\xfd\x01' \
'\xb0\xc6\x86\x8b\xdd\xae\x80\xf3\xa9\x9fd\x16\n\x00R%\x1a\x06' \
'\xe9\xd8b\x98\x1d\xf4\xf3+\x9bf\x01\xd8p\x1b\xf3.\xed\x9f^g\xc3' \
'^\xd9W81T\xdb\xd5\x04sx|\xf2\xeb\xd6`%?x\xed"\x831\xbf\xf3\xdc' \
'b\xeb%gaY\xe1\xad\x9f\xb9f\'1w\xa9\xa5a\x83s\x82J\xb98\xbc4\x8b' \
'\x83\x00\x9f$z\xb8#\xa5\xb1\xdf\x98\xd9\xec\x1b\x89O\xe3Ts\x9a4' \
'\x17m\x8b\xfc\x8f\xa5\x95\x9a\xfc\xfa\xed,\xe5|\xa1\xfe\x15\xb9' \
'\xbc\xb2\x93\x1f\xf2\x95\xff\xdf,\x1a\xc5\xe7\x17*\x93Oz:>\x0e'
data_non_inlined = '\x00\x00\x00\x01\x00\x00\x00\x00\x00\x01D\x19' \
'\x00\x07e\x12\x00\x00\x00\x00\x00\x00\x00\x00\xff\xff\xff\xff' \
'\xff\xff\xff\xff\xd1\xf4\xbb\xb0\xbe\xfc\x13\xbd\x8c\xd3\x9d' \
'\x0f\xcd\xd9;\x8c\x07\x8cJ/\x00\x00\x00\x00\x00\x00\x00\x00\x00' \
'\x00\x00\x00\x00\x00\x00\x01D\x19\x00\x00\x00\x00\x00\xdf\x00' \
'\x00\x01q\x00\x00\x00\x01\x00\x00\x00\x01\x00\x00\x00\x00\xff' \
'\xff\xff\xff\xc1\x12\xb9\x04\x96\xa4Z1t\x91\xdfsJ\x90\xf0\x9bh' \
'\x07l&\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00' \
'\x00\x01D\xf8\x00\x00\x00\x00\x01\x1b\x00\x00\x01\xb8\x00\x00' \
'\x00\x01\x00\x00\x00\x02\x00\x00\x00\x01\xff\xff\xff\xff\x02\n' \
'\x0e\xc6&\xa1\x92\xae6\x0b\x02i\xfe-\xe5\xbao\x05\xd1\xe7\x00' \
'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01F' \
'\x13\x00\x00\x00\x00\x01\xec\x00\x00\x03\x06\x00\x00\x00\x01' \
'\x00\x00\x00\x03\x00\x00\x00\x02\xff\xff\xff\xff\x12\xcb\xeby1' \
'\xb6\r\x98B\xcb\x07\xbd`\x8f\x92\xd9\xc4\x84\xbdK\x00\x00\x00' \
'\x00\x00\x00\x00\x00\x00\x00\x00\x00'
def parse_index2(data, inline):
index, chunkcache = parsers.parse_index2(data, inline)
return list(index), chunkcache
def importparsers(hexversion):
"""Import mercurial.parsers with the given sys.hexversion."""
# The file parsers.c inspects sys.hexversion to determine the version
# of the currently-running Python interpreter, so we monkey-patch
# sys.hexversion to simulate using different versions.
code = ("import sys; sys.hexversion=%s; "
"import mercurial.cext.parsers" % hexversion)
cmd = "python -c \"%s\"" % code
# We need to do these tests inside a subprocess because parser.c's
# version-checking code happens inside the module init function, and
# when using reload() to reimport an extension module, "The init function
# of extension modules is not called a second time"
# (from http://docs.python.org/2/library/functions.html?#reload).
p = subprocess.Popen(cmd, shell=True,
stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
return p.communicate() # returns stdout, stderr
def printhexfail(testnumber, hexversion, stdout, expected):
try:
hexstring = hex(hexversion)
except TypeError:
hexstring = None
print("FAILED: version test #%s with Python %s and patched "
"sys.hexversion %r (%r):\n Expected %s but got:\n-->'%s'\n" %
(testnumber, sys.version_info, hexversion, hexstring, expected,
stdout))
def testversionokay(testnumber, hexversion):
stdout, stderr = importparsers(hexversion)
if stdout:
printhexfail(testnumber, hexversion, stdout, expected="no stdout")
def testversionfail(testnumber, hexversion):
stdout, stderr = importparsers(hexversion)
# We include versionerrortext to distinguish from other ImportErrors.
errtext = "ImportError: %s" % parsers.versionerrortext
if errtext not in stdout:
printhexfail(testnumber, hexversion, stdout,
expected="stdout to contain %r" % errtext)
def makehex(major, minor, micro):
return int("%x%02x%02x00" % (major, minor, micro), 16)
def runversiontests():
"""Check the version-detection logic when importing parsers."""
info = sys.version_info
major, minor, micro = info[0], info[1], info[2]
# Test same major-minor versions.
testversionokay(1, makehex(major, minor, micro))
testversionokay(2, makehex(major, minor, micro + 1))
# Test different major-minor versions.
testversionfail(3, makehex(major + 1, minor, micro))
testversionfail(4, makehex(major, minor + 1, micro))
testversionfail(5, "'foo'")
def runtest() :
# Only test the version-detection logic if it is present.
try:
parsers.versionerrortext
except AttributeError:
pass
else:
runversiontests()
# Check that parse_index2() raises TypeError on bad arguments.
try:
parse_index2(0, True)
except TypeError:
pass
else:
print("Expected to get TypeError.")
# Check parsers.parse_index2() on an index file against the original
# Python implementation of parseindex, both with and without inlined data.
py_res_1 = py_parseindex(data_inlined, True)
c_res_1 = parse_index2(data_inlined, True)
py_res_2 = py_parseindex(data_non_inlined, False)
c_res_2 = parse_index2(data_non_inlined, False)
if py_res_1 != c_res_1:
print("Parse index result (with inlined data) differs!")
if py_res_2 != c_res_2:
print("Parse index result (no inlined data) differs!")
ix = parsers.parse_index2(data_inlined, True)[0]
for i, r in enumerate(ix):
if r[7] == nullid:
i = -1
try:
if ix[r[7]] != i:
print('Reverse lookup inconsistent for %r'
% r[7].encode('hex'))
except TypeError:
# pure version doesn't support this
break
print("done")
runtest()