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bpo-33671 / shutil.copyfile: use memoryview() with dynamic size on Windows (#7681) 

bpo-33671
* use memoryview() with size == file size on Windows, see https://github.com/python/cpython/pull/7160#discussion_r195405230
* release intermediate (sliced) memoryview immediately
* replace "OSX" occurrences with "macOS"
* add some unittests for copyfileobj()
This commit is contained in:
Giampaolo Rodola 2018-06-19 08:27:29 -07:00 committed by GitHub
parent 936f03e7fa
commit c7f02a9659
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7 changed files with 156 additions and 67 deletions
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6
Doc/library/shutil.rst
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@ -407,11 +407,15 @@ efficiently (see :issue:`33671`).
"fast-copy" means that the copying operation occurs within the kernel, avoiding
the use of userspace buffers in Python as in "``outfd.write(infd.read())``".
On OSX `fcopyfile`_ is used to copy the file content (not metadata).
On macOS `fcopyfile`_ is used to copy the file content (not metadata).
On Linux, Solaris and other POSIX platforms where :func:`os.sendfile` supports
copies between 2 regular file descriptors :func:`os.sendfile` is used.
On Windows :func:`shutil.copyfile` uses a bigger default buffer size (1 MiB
instead of 16 KiB) and a :func:`memoryview`-based variant of
:func:`shutil.copyfileobj` is used.
If the fast-copy operation fails and no data was written in the destination
file then shutil will silently fallback on using less efficient
:func:`copyfileobj` function internally.

28
Doc/whatsnew/3.8.rst
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@ -95,20 +95,18 @@ Optimizations
* :func:`shutil.copyfile`, :func:`shutil.copy`, :func:`shutil.copy2`,
:func:`shutil.copytree` and :func:`shutil.move` use platform-specific
"fast-copy" syscalls on Linux, OSX and Solaris in order to copy the file more
efficiently.
"fast-copy" syscalls on Linux, macOS and Solaris in order to copy the file
more efficiently.
"fast-copy" means that the copying operation occurs within the kernel,
avoiding the use of userspace buffers in Python as in
"``outfd.write(infd.read())``".
All other platforms not using such technique will rely on a faster
:func:`shutil.copyfile` implementation using :func:`memoryview`,
:class:`bytearray` and
:meth:`BufferedIOBase.readinto() <io.BufferedIOBase.readinto>`.
Finally, :func:`shutil.copyfile` default buffer size on Windows was increased
from 16KB to 1MB.
The speedup for copying a 512MB file within the same partition is about +26%
on Linux, +50% on OSX and +38% on Windows. Also, much less CPU cycles are
consumed.
On Windows :func:`shutil.copyfile` uses a bigger default buffer size (1 MiB
instead of 16 KiB) and a :func:`memoryview`-based variant of
:func:`shutil.copyfileobj` is used.
The speedup for copying a 512 MiB file within the same partition is about
+26% on Linux, +50% on macOS and +40% on Windows. Also, much less CPU cycles
are consumed.
See :ref:`shutil-platform-dependent-efficient-copy-operations` section.
(Contributed by Giampaolo Rodola' in :issue:`25427`.)
* The default protocol in the :mod:`pickle` module is now Protocol 4,
@ -179,6 +177,14 @@ Changes in the Python API
* The :class:`cProfile.Profile` class can now be used as a context
manager. (Contributed by Scott Sanderson in :issue:`29235`.)
* :func:`shutil.copyfile`, :func:`shutil.copy`, :func:`shutil.copy2`,
:func:`shutil.copytree` and :func:`shutil.move` use platform-specific
"fast-copy" syscalls (see
:ref:`shutil-platform-dependent-efficient-copy-operations` section).
* :func:`shutil.copyfile` default buffer size on Windows was changed from
16 KiB to 1 MiB.
CPython bytecode changes
------------------------

78
Lib/shutil.py
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@ -43,15 +43,16 @@ try:
except ImportError:
getgrnam = None
_WINDOWS = os.name == 'nt'
posix = nt = None
if os.name == 'posix':
import posix
elif os.name == 'nt':
elif _WINDOWS:
import nt
COPY_BUFSIZE = 1024 * 1024 if os.name == 'nt' else 16 * 1024
COPY_BUFSIZE = 1024 * 1024 if _WINDOWS else 16 * 1024
_HAS_SENDFILE = posix and hasattr(os, "sendfile")
_HAS_FCOPYFILE = posix and hasattr(posix, "_fcopyfile") # OSX
_HAS_FCOPYFILE = posix and hasattr(posix, "_fcopyfile") # macOS
__all__ = ["copyfileobj", "copyfile", "copymode", "copystat", "copy", "copy2",
"copytree", "move", "rmtree", "Error", "SpecialFileError",
@ -88,9 +89,9 @@ class _GiveupOnFastCopy(Exception):
file copy when fast-copy functions fail to do so.
"""
def _fastcopy_osx(fsrc, fdst, flags):
def _fastcopy_fcopyfile(fsrc, fdst, flags):
"""Copy a regular file content or metadata by using high-performance
fcopyfile(3) syscall (OSX).
fcopyfile(3) syscall (macOS).
"""
try:
infd = fsrc.fileno()
@ -168,8 +169,11 @@ def _fastcopy_sendfile(fsrc, fdst):
break # EOF
offset += sent
def _copybinfileobj(fsrc, fdst, length=COPY_BUFSIZE):
"""Copy 2 regular file objects open in binary mode."""
def _copyfileobj_readinto(fsrc, fdst, length=COPY_BUFSIZE):
"""readinto()/memoryview() based variant of copyfileobj().
*fsrc* must support readinto() method and both files must be
open in binary mode.
"""
# Localize variable access to minimize overhead.
fsrc_readinto = fsrc.readinto
fdst_write = fdst.write
@ -179,28 +183,21 @@ def _copybinfileobj(fsrc, fdst, length=COPY_BUFSIZE):
if not n:
break
elif n < length:
fdst_write(mv[:n])
with mv[:n] as smv:
fdst.write(smv)
else:
fdst_write(mv)
def _is_binary_files_pair(fsrc, fdst):
return hasattr(fsrc, 'readinto') and \
isinstance(fsrc, io.BytesIO) or 'b' in getattr(fsrc, 'mode', '') and \
isinstance(fdst, io.BytesIO) or 'b' in getattr(fdst, 'mode', '')
def copyfileobj(fsrc, fdst, length=COPY_BUFSIZE):
"""copy data from file-like object fsrc to file-like object fdst"""
if _is_binary_files_pair(fsrc, fdst):
_copybinfileobj(fsrc, fdst, length=length)
else:
# Localize variable access to minimize overhead.
fsrc_read = fsrc.read
fdst_write = fdst.write
while 1:
buf = fsrc_read(length)
if not buf:
break
fdst_write(buf)
# Localize variable access to minimize overhead.
fsrc_read = fsrc.read
fdst_write = fdst.write
while True:
buf = fsrc_read(length)
if not buf:
break
fdst_write(buf)
def _samefile(src, dst):
# Macintosh, Unix.
@ -215,7 +212,7 @@ def _samefile(src, dst):
os.path.normcase(os.path.abspath(dst)))
def copyfile(src, dst, *, follow_symlinks=True):
"""Copy data from src to dst.
"""Copy data from src to dst in the most efficient way possible.
If follow_symlinks is not set and src is a symbolic link, a new
symlink will be created instead of copying the file it points to.
@ -224,7 +221,8 @@ def copyfile(src, dst, *, follow_symlinks=True):
if _samefile(src, dst):
raise SameFileError("{!r} and {!r} are the same file".format(src, dst))
for fn in [src, dst]:
file_size = 0
for i, fn in enumerate([src, dst]):
try:
st = os.stat(fn)
except OSError:
@ -234,26 +232,34 @@ def copyfile(src, dst, *, follow_symlinks=True):
# XXX What about other special files? (sockets, devices...)
if stat.S_ISFIFO(st.st_mode):
raise SpecialFileError("`%s` is a named pipe" % fn)
if _WINDOWS and i == 0:
file_size = st.st_size
if not follow_symlinks and os.path.islink(src):
os.symlink(os.readlink(src), dst)
else:
with open(src, 'rb') as fsrc, open(dst, 'wb') as fdst:
if _HAS_SENDFILE:
# macOS
if _HAS_FCOPYFILE:
try:
_fastcopy_fcopyfile(fsrc, fdst, posix._COPYFILE_DATA)
return dst
except _GiveupOnFastCopy:
pass
# Linux / Solaris
elif _HAS_SENDFILE:
try:
_fastcopy_sendfile(fsrc, fdst)
return dst
except _GiveupOnFastCopy:
pass
# Windows, see:
# https://github.com/python/cpython/pull/7160#discussion_r195405230
elif _WINDOWS and file_size > 0:
_copyfileobj_readinto(fsrc, fdst, min(file_size, COPY_BUFSIZE))
return dst
if _HAS_FCOPYFILE:
try:
_fastcopy_osx(fsrc, fdst, posix._COPYFILE_DATA)
return dst
except _GiveupOnFastCopy:
pass
_copybinfileobj(fsrc, fdst)
copyfileobj(fsrc, fdst)
return dst
@ -1147,7 +1153,7 @@ if hasattr(os, 'statvfs'):
used = (st.f_blocks - st.f_bfree) * st.f_frsize
return _ntuple_diskusage(total, used, free)
elif os.name == 'nt':
elif _WINDOWS:
__all__.append('disk_usage')
_ntuple_diskusage = collections.namedtuple('usage', 'total used free')

88
Lib/test/test_shutil.py
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@ -33,7 +33,7 @@ from test import support
from test.support import TESTFN, FakePath
TESTFN2 = TESTFN + "2"
OSX = sys.platform.startswith("darwin")
MACOS = sys.platform.startswith("darwin")
try:
import grp
import pwd
@ -1808,7 +1808,7 @@ class TestCopyFile(unittest.TestCase):
self.assertRaises(OSError, shutil.copyfile, 'srcfile', 'destfile')
@unittest.skipIf(OSX, "skipped on OSX")
@unittest.skipIf(MACOS, "skipped on macOS")
def test_w_dest_open_fails(self):
srcfile = self.Faux()
@ -1828,7 +1828,7 @@ class TestCopyFile(unittest.TestCase):
self.assertEqual(srcfile._exited_with[1].args,
('Cannot open "destfile"',))
@unittest.skipIf(OSX, "skipped on OSX")
@unittest.skipIf(MACOS, "skipped on macOS")
def test_w_dest_close_fails(self):
srcfile = self.Faux()
@ -1851,7 +1851,7 @@ class TestCopyFile(unittest.TestCase):
self.assertEqual(srcfile._exited_with[1].args,
('Cannot close',))
@unittest.skipIf(OSX, "skipped on OSX")
@unittest.skipIf(MACOS, "skipped on macOS")
def test_w_source_close_fails(self):
srcfile = self.Faux(True)
@ -1892,6 +1892,80 @@ class TestCopyFile(unittest.TestCase):
os.rmdir(dst_dir)
class TestCopyFileObj(unittest.TestCase):
FILESIZE = 2 * 1024 * 1024
@classmethod
def setUpClass(cls):
write_test_file(TESTFN, cls.FILESIZE)
@classmethod
def tearDownClass(cls):
support.unlink(TESTFN)
support.unlink(TESTFN2)
def tearDown(self):
support.unlink(TESTFN2)
@contextlib.contextmanager
def get_files(self):
with open(TESTFN, "rb") as src:
with open(TESTFN2, "wb") as dst:
yield (src, dst)
def assert_files_eq(self, src, dst):
with open(src, 'rb') as fsrc:
with open(dst, 'rb') as fdst:
self.assertEqual(fsrc.read(), fdst.read())
def test_content(self):
with self.get_files() as (src, dst):
shutil.copyfileobj(src, dst)
self.assert_files_eq(TESTFN, TESTFN2)
def test_file_not_closed(self):
with self.get_files() as (src, dst):
shutil.copyfileobj(src, dst)
assert not src.closed
assert not dst.closed
def test_file_offset(self):
with self.get_files() as (src, dst):
shutil.copyfileobj(src, dst)
self.assertEqual(src.tell(), self.FILESIZE)
self.assertEqual(dst.tell(), self.FILESIZE)
@unittest.skipIf(os.name != 'nt', "Windows only")
def test_win_impl(self):
# Make sure alternate Windows implementation is called.
with unittest.mock.patch("shutil._copyfileobj_readinto") as m:
shutil.copyfile(TESTFN, TESTFN2)
assert m.called
# File size is 2 MiB but max buf size should be 1 MiB.
self.assertEqual(m.call_args[0][2], 1 * 1024 * 1024)
# If file size < 1 MiB memoryview() length must be equal to
# the actual file size.
with tempfile.NamedTemporaryFile(delete=False) as f:
f.write(b'foo')
fname = f.name
self.addCleanup(support.unlink, fname)
with unittest.mock.patch("shutil._copyfileobj_readinto") as m:
shutil.copyfile(fname, TESTFN2)
self.assertEqual(m.call_args[0][2], 3)
# Empty files should not rely on readinto() variant.
with tempfile.NamedTemporaryFile(delete=False) as f:
pass
fname = f.name
self.addCleanup(support.unlink, fname)
with unittest.mock.patch("shutil._copyfileobj_readinto") as m:
shutil.copyfile(fname, TESTFN2)
assert not m.called
self.assert_files_eq(fname, TESTFN2)
class _ZeroCopyFileTest(object):
"""Tests common to all zero-copy APIs."""
FILESIZE = (10 * 1024 * 1024) # 10 MiB
@ -2111,12 +2185,12 @@ class TestZeroCopySendfile(_ZeroCopyFileTest, unittest.TestCase):
shutil._HAS_SENDFILE = True
@unittest.skipIf(not OSX, 'OSX only')
class TestZeroCopyOSX(_ZeroCopyFileTest, unittest.TestCase):
@unittest.skipIf(not MACOS, 'macOS only')
class TestZeroCopyMACOS(_ZeroCopyFileTest, unittest.TestCase):
PATCHPOINT = "posix._fcopyfile"
def zerocopy_fun(self, src, dst):
return shutil._fastcopy_osx(src, dst, posix._COPYFILE_DATA)
return shutil._fastcopy_fcopyfile(src, dst, posix._COPYFILE_DATA)
class TermsizeTests(unittest.TestCase):

15
Misc/NEWS.d/next/Library/2018-05-28-23-25-17.bpo-33671.GIdKKi.rst
View File

@ -1,11 +1,10 @@
:func:`shutil.copyfile`, :func:`shutil.copy`, :func:`shutil.copy2`,
:func:`shutil.copytree` and :func:`shutil.move` use platform-specific
fast-copy syscalls on Linux, Solaris and OSX in order to copy the file
more efficiently. All other platforms not using such technique will rely on a
faster :func:`shutil.copyfile` implementation using :func:`memoryview`,
:class:`bytearray` and
:meth:`BufferedIOBase.readinto() <io.BufferedIOBase.readinto>`.
Finally, :func:`shutil.copyfile` default buffer size on Windows was increased
from 16KB to 1MB. The speedup for copying a 512MB file is about +26% on Linux,
+50% on OSX and +38% on Windows. Also, much less CPU cycles are consumed
fast-copy syscalls on Linux, Solaris and macOS in order to copy the file
more efficiently.
On Windows :func:`shutil.copyfile` uses a bigger default buffer size (1 MiB
instead of 16 KiB) and a :func:`memoryview`-based variant of
:func:`shutil.copyfileobj` is used.
The speedup for copying a 512MiB file is about +26% on Linux, +50% on macOS and
+40% on Windows. Also, much less CPU cycles are consumed.
(Contributed by Giampaolo Rodola' in :issue:`25427`.)

4
Modules/clinic/posixmodule.c.h generated
View File

@ -3859,7 +3859,7 @@ PyDoc_STRVAR(os__fcopyfile__doc__,
"_fcopyfile($module, infd, outfd, flags, /)\n"
"--\n"
"\n"
"Efficiently copy content or metadata of 2 regular file descriptors (OSX).");
"Efficiently copy content or metadata of 2 regular file descriptors (macOS).");
#define OS__FCOPYFILE_METHODDEF \
{"_fcopyfile", (PyCFunction)os__fcopyfile, METH_FASTCALL, os__fcopyfile__doc__},
@ -6627,4 +6627,4 @@ exit:
#ifndef OS_GETRANDOM_METHODDEF
#define OS_GETRANDOM_METHODDEF
#endif /* !defined(OS_GETRANDOM_METHODDEF) */
/*[clinic end generated code: output=b5d1ec71bc6f0651 input=a9049054013a1b77]*/
/*[clinic end generated code: output=47fb6a3e88cba6d9 input=a9049054013a1b77]*/

4
Modules/posixmodule.c
View File

@ -8774,12 +8774,12 @@ os._fcopyfile
flags: int
/
Efficiently copy content or metadata of 2 regular file descriptors (OSX).
Efficiently copy content or metadata of 2 regular file descriptors (macOS).
[clinic start generated code]*/
static PyObject *
os__fcopyfile_impl(PyObject *module, int infd, int outfd, int flags)
/*[clinic end generated code: output=8e8885c721ec38e3 input=aeb9456804eec879]*/
/*[clinic end generated code: output=8e8885c721ec38e3 input=69e0770e600cb44f]*/
{
int ret;