view mercurial/store.py @ 42745:4d20b1fe8a72

rust-discovery: using from Python code

As previously done in other topics, the Rust version is used if it's been
built.

The version fully in Rust of the partialdiscovery class has the performance
advantage over the Python version (actually using the Rust MissingAncestor) if
the undecided set is big enough. Otherwise no sampling occurs, and the
discovery is reasonably fast anyway.

Note: it's hard to predict the size of the initial undecided set, it can
depend on the kind of topological changes between the local and remote graphs.
The point of the Rust version is to make the bad cases acceptable.

More specifically, the performance advantages are:

- faster sampling, especially takefullsample()
- much faster addmissings() in almost all cases (see commit message in
  grandparent of the present changeset)
- no conversion cost of the undecided set at the interface between Rust and
  Python

== Measurements with big undecided sets

For an extreme example, discovery between mozilla-try and mozilla-unified
(over one million undecided revisions, same case as in dbd0fcca6dfc), we
get roughly a x2.5/x3 better performance:

Growing sample size (5% starting with 200): time goes down from
210 to 72 seconds.
Constant sample size of 200: time down from 1853 to 659 seconds.

With a sample size computed from number of roots and heads of the
undecided set (`respectsize` is `False`), here are perfdiscovery results:

Before ! wall 9.358729 comb 9.360000 user 9.310000 sys 0.050000 (median of 50)
After  ! wall 3.793819 comb 3.790000 user 3.750000 sys 0.040000 (median of 50)

In that later case, the sample sizes are routinely in the hundreds of
thousands of revisions. While still faster, the Rust iteration in
addmissings has less of an advantage than with smaller sample sizes, but
one sees addcommons becoming faster, probably a consequence of not having
to copy big sets back and forth.

This example is not a goal in itself, but it showcases several different
areas in which the process can become slow, due to different factors, and
how this full Rust version can help.

== Measurements with small undecided sets

In cases the undecided set is small enough than no sampling occurs,
the Rust version has a disadvantage at init if `targetheads` is really big
(some time is lost in the translation to Rust data structures),
and that is compensated by the faster `addmissings()`.

On a private repository with over one million commits, we still get a minor
improvement, of 6.8%:

  Before ! wall 0.593585 comb 0.590000 user 0.550000 sys 0.040000 (median of 50)
  After  ! wall 0.553035 comb 0.550000 user 0.520000 sys 0.030000 (median of 50)

What's interesting in that case is the first addinfo() at 180ms for Rust and
233ms for Python+C, mostly due to add_missings and the children cache
computation being done in less than 0.2ms on the Rust side vs over 40ms on the
Python side.

The worst case we have on hand is with mozilla-try, prepared with
discovery-helper.sh for 10 heads and depth 10, time goes up 2.2% on the median.
In this case `targetheads` is really huge with 165842 server heads.

  Before ! wall 0.823884 comb 0.810000 user 0.790000 sys 0.020000 (median of 50)
  After  ! wall 0.842607 comb 0.840000 user 0.800000 sys 0.040000 (median of 50)

If that would be considered a problem, more adjustments can be made, which are
prematurate at this stage: cooking special variants of methods of the inner
MissingAncestors object, retrieving local heads directly from Rust to avoid
the cost of conversion. Effort would probably be better spent at this point
improving the surroundings if needed.

Here's another data point with a smaller repository, pypy, where performance
is almost identical

 Before ! wall 0.015121 comb 0.030000 user 0.020000 sys 0.010000 (median of 186)
 After  ! wall 0.015009 comb 0.010000 user 0.010000 sys 0.000000 (median of 184)

Differential Revision: https://phab.mercurial-scm.org/D6430

# store.py - repository store handling for Mercurial
#
# Copyright 2008 Matt Mackall <[e-mail]>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

from __future__ import absolute_import

import errno
import functools
import hashlib
import os
import stat

from .i18n import _
from . import (
    error,
    node,
    policy,
    pycompat,
    util,
    vfs as vfsmod,
)

parsers = policy.importmod(r'parsers')
# how much bytes should be read from fncache in one read
# It is done to prevent loading large fncache files into memory
fncache_chunksize = 10 ** 6

def _matchtrackedpath(path, matcher):
    """parses a fncache entry and returns whether the entry is tracking a path
    matched by matcher or not.

    If matcher is None, returns True"""

    if matcher is None:
        return True
    path = decodedir(path)
    if path.startswith('data/'):
        return matcher(path[len('data/'):-len('.i')])
    elif path.startswith('meta/'):
        return matcher.visitdir(path[len('meta/'):-len('/00manifest.i')])

    raise error.ProgrammingError("cannot decode path %s" % path)

# This avoids a collision between a file named foo and a dir named
# foo.i or foo.d
def _encodedir(path):
    '''
    >>> _encodedir(b'data/foo.i')
    'data/foo.i'
    >>> _encodedir(b'data/foo.i/bla.i')
    'data/foo.i.hg/bla.i'
    >>> _encodedir(b'data/foo.i.hg/bla.i')
    'data/foo.i.hg.hg/bla.i'
    >>> _encodedir(b'data/foo.i\\ndata/foo.i/bla.i\\ndata/foo.i.hg/bla.i\\n')
    'data/foo.i\\ndata/foo.i.hg/bla.i\\ndata/foo.i.hg.hg/bla.i\\n'
    '''
    return (path
            .replace(".hg/", ".hg.hg/")
            .replace(".i/", ".i.hg/")
            .replace(".d/", ".d.hg/"))

encodedir = getattr(parsers, 'encodedir', _encodedir)

def decodedir(path):
    '''
    >>> decodedir(b'data/foo.i')
    'data/foo.i'
    >>> decodedir(b'data/foo.i.hg/bla.i')
    'data/foo.i/bla.i'
    >>> decodedir(b'data/foo.i.hg.hg/bla.i')
    'data/foo.i.hg/bla.i'
    '''
    if ".hg/" not in path:
        return path
    return (path
            .replace(".d.hg/", ".d/")
            .replace(".i.hg/", ".i/")
            .replace(".hg.hg/", ".hg/"))

def _reserved():
    ''' characters that are problematic for filesystems

    * ascii escapes (0..31)
    * ascii hi (126..255)
    * windows specials

    these characters will be escaped by encodefunctions
    '''
    winreserved = [ord(x) for x in u'\\:*?"<>|']
    for x in range(32):
        yield x
    for x in range(126, 256):
        yield x
    for x in winreserved:
        yield x

def _buildencodefun():
    '''
    >>> enc, dec = _buildencodefun()

    >>> enc(b'nothing/special.txt')
    'nothing/special.txt'
    >>> dec(b'nothing/special.txt')
    'nothing/special.txt'

    >>> enc(b'HELLO')
    '_h_e_l_l_o'
    >>> dec(b'_h_e_l_l_o')
    'HELLO'

    >>> enc(b'hello:world?')
    'hello~3aworld~3f'
    >>> dec(b'hello~3aworld~3f')
    'hello:world?'

    >>> enc(b'the\\x07quick\\xADshot')
    'the~07quick~adshot'
    >>> dec(b'the~07quick~adshot')
    'the\\x07quick\\xadshot'
    '''
    e = '_'
    xchr = pycompat.bytechr
    asciistr = list(map(xchr, range(127)))
    capitals = list(range(ord("A"), ord("Z") + 1))

    cmap = dict((x, x) for x in asciistr)
    for x in _reserved():
        cmap[xchr(x)] = "~%02x" % x
    for x in capitals + [ord(e)]:
        cmap[xchr(x)] = e + xchr(x).lower()

    dmap = {}
    for k, v in cmap.iteritems():
        dmap[v] = k
    def decode(s):
        i = 0
        while i < len(s):
            for l in pycompat.xrange(1, 4):
                try:
                    yield dmap[s[i:i + l]]
                    i += l
                    break
                except KeyError:
                    pass
            else:
                raise KeyError
    return (lambda s: ''.join([cmap[s[c:c + 1]]
                               for c in pycompat.xrange(len(s))]),
            lambda s: ''.join(list(decode(s))))

_encodefname, _decodefname = _buildencodefun()

def encodefilename(s):
    '''
    >>> encodefilename(b'foo.i/bar.d/bla.hg/hi:world?/HELLO')
    'foo.i.hg/bar.d.hg/bla.hg.hg/hi~3aworld~3f/_h_e_l_l_o'
    '''
    return _encodefname(encodedir(s))

def decodefilename(s):
    '''
    >>> decodefilename(b'foo.i.hg/bar.d.hg/bla.hg.hg/hi~3aworld~3f/_h_e_l_l_o')
    'foo.i/bar.d/bla.hg/hi:world?/HELLO'
    '''
    return decodedir(_decodefname(s))

def _buildlowerencodefun():
    '''
    >>> f = _buildlowerencodefun()
    >>> f(b'nothing/special.txt')
    'nothing/special.txt'
    >>> f(b'HELLO')
    'hello'
    >>> f(b'hello:world?')
    'hello~3aworld~3f'
    >>> f(b'the\\x07quick\\xADshot')
    'the~07quick~adshot'
    '''
    xchr = pycompat.bytechr
    cmap = dict([(xchr(x), xchr(x)) for x in pycompat.xrange(127)])
    for x in _reserved():
        cmap[xchr(x)] = "~%02x" % x
    for x in range(ord("A"), ord("Z") + 1):
        cmap[xchr(x)] = xchr(x).lower()
    def lowerencode(s):
        return "".join([cmap[c] for c in pycompat.iterbytestr(s)])
    return lowerencode

lowerencode = getattr(parsers, 'lowerencode', None) or _buildlowerencodefun()

# Windows reserved names: con, prn, aux, nul, com1..com9, lpt1..lpt9
_winres3 = ('aux', 'con', 'prn', 'nul') # length 3
_winres4 = ('com', 'lpt')               # length 4 (with trailing 1..9)
def _auxencode(path, dotencode):
    '''
    Encodes filenames containing names reserved by Windows or which end in
    period or space. Does not touch other single reserved characters c.
    Specifically, c in '\\:*?"<>|' or ord(c) <= 31 are *not* encoded here.
    Additionally encodes space or period at the beginning, if dotencode is
    True. Parameter path is assumed to be all lowercase.
    A segment only needs encoding if a reserved name appears as a
    basename (e.g. "aux", "aux.foo"). A directory or file named "foo.aux"
    doesn't need encoding.

    >>> s = b'.foo/aux.txt/txt.aux/con/prn/nul/foo.'
    >>> _auxencode(s.split(b'/'), True)
    ['~2efoo', 'au~78.txt', 'txt.aux', 'co~6e', 'pr~6e', 'nu~6c', 'foo~2e']
    >>> s = b'.com1com2/lpt9.lpt4.lpt1/conprn/com0/lpt0/foo.'
    >>> _auxencode(s.split(b'/'), False)
    ['.com1com2', 'lp~749.lpt4.lpt1', 'conprn', 'com0', 'lpt0', 'foo~2e']
    >>> _auxencode([b'foo. '], True)
    ['foo.~20']
    >>> _auxencode([b' .foo'], True)
    ['~20.foo']
    '''
    for i, n in enumerate(path):
        if not n:
            continue
        if dotencode and n[0] in '. ':
            n = "~%02x" % ord(n[0:1]) + n[1:]
            path[i] = n
        else:
            l = n.find('.')
            if l == -1:
                l = len(n)
            if ((l == 3 and n[:3] in _winres3) or
                (l == 4 and n[3:4] <= '9' and n[3:4] >= '1'
                        and n[:3] in _winres4)):
                # encode third letter ('aux' -> 'au~78')
                ec = "~%02x" % ord(n[2:3])
                n = n[0:2] + ec + n[3:]
                path[i] = n
        if n[-1] in '. ':
            # encode last period or space ('foo...' -> 'foo..~2e')
            path[i] = n[:-1] + "~%02x" % ord(n[-1:])
    return path

_maxstorepathlen = 120
_dirprefixlen = 8
_maxshortdirslen = 8 * (_dirprefixlen + 1) - 4

def _hashencode(path, dotencode):
    digest = node.hex(hashlib.sha1(path).digest())
    le = lowerencode(path[5:]).split('/') # skips prefix 'data/' or 'meta/'
    parts = _auxencode(le, dotencode)
    basename = parts[-1]
    _root, ext = os.path.splitext(basename)
    sdirs = []
    sdirslen = 0
    for p in parts[:-1]:
        d = p[:_dirprefixlen]
        if d[-1] in '. ':
            # Windows can't access dirs ending in period or space
            d = d[:-1] + '_'
        if sdirslen == 0:
            t = len(d)
        else:
            t = sdirslen + 1 + len(d)
            if t > _maxshortdirslen:
                break
        sdirs.append(d)
        sdirslen = t
    dirs = '/'.join(sdirs)
    if len(dirs) > 0:
        dirs += '/'
    res = 'dh/' + dirs + digest + ext
    spaceleft = _maxstorepathlen - len(res)
    if spaceleft > 0:
        filler = basename[:spaceleft]
        res = 'dh/' + dirs + filler + digest + ext
    return res

def _hybridencode(path, dotencode):
    '''encodes path with a length limit

    Encodes all paths that begin with 'data/', according to the following.

    Default encoding (reversible):

    Encodes all uppercase letters 'X' as '_x'. All reserved or illegal
    characters are encoded as '~xx', where xx is the two digit hex code
    of the character (see encodefilename).
    Relevant path components consisting of Windows reserved filenames are
    masked by encoding the third character ('aux' -> 'au~78', see _auxencode).

    Hashed encoding (not reversible):

    If the default-encoded path is longer than _maxstorepathlen, a
    non-reversible hybrid hashing of the path is done instead.
    This encoding uses up to _dirprefixlen characters of all directory
    levels of the lowerencoded path, but not more levels than can fit into
    _maxshortdirslen.
    Then follows the filler followed by the sha digest of the full path.
    The filler is the beginning of the basename of the lowerencoded path
    (the basename is everything after the last path separator). The filler
    is as long as possible, filling in characters from the basename until
    the encoded path has _maxstorepathlen characters (or all chars of the
    basename have been taken).
    The extension (e.g. '.i' or '.d') is preserved.

    The string 'data/' at the beginning is replaced with 'dh/', if the hashed
    encoding was used.
    '''
    path = encodedir(path)
    ef = _encodefname(path).split('/')
    res = '/'.join(_auxencode(ef, dotencode))
    if len(res) > _maxstorepathlen:
        res = _hashencode(path, dotencode)
    return res

def _pathencode(path):
    de = encodedir(path)
    if len(path) > _maxstorepathlen:
        return _hashencode(de, True)
    ef = _encodefname(de).split('/')
    res = '/'.join(_auxencode(ef, True))
    if len(res) > _maxstorepathlen:
        return _hashencode(de, True)
    return res

_pathencode = getattr(parsers, 'pathencode', _pathencode)

def _plainhybridencode(f):
    return _hybridencode(f, False)

def _calcmode(vfs):
    try:
        # files in .hg/ will be created using this mode
        mode = vfs.stat().st_mode
            # avoid some useless chmods
        if (0o777 & ~util.umask) == (0o777 & mode):
            mode = None
    except OSError:
        mode = None
    return mode

_data = ('bookmarks narrowspec data meta 00manifest.d 00manifest.i'
         ' 00changelog.d 00changelog.i phaseroots obsstore')

def isrevlog(f, kind, st):
    return kind == stat.S_IFREG and f[-2:] in ('.i', '.d')

class basicstore(object):
    '''base class for local repository stores'''
    def __init__(self, path, vfstype):
        vfs = vfstype(path)
        self.path = vfs.base
        self.createmode = _calcmode(vfs)
        vfs.createmode = self.createmode
        self.rawvfs = vfs
        self.vfs = vfsmod.filtervfs(vfs, encodedir)
        self.opener = self.vfs

    def join(self, f):
        return self.path + '/' + encodedir(f)

    def _walk(self, relpath, recurse, filefilter=isrevlog):
        '''yields (unencoded, encoded, size)'''
        path = self.path
        if relpath:
            path += '/' + relpath
        striplen = len(self.path) + 1
        l = []
        if self.rawvfs.isdir(path):
            visit = [path]
            readdir = self.rawvfs.readdir
            while visit:
                p = visit.pop()
                for f, kind, st in readdir(p, stat=True):
                    fp = p + '/' + f
                    if filefilter(f, kind, st):
                        n = util.pconvert(fp[striplen:])
                        l.append((decodedir(n), n, st.st_size))
                    elif kind == stat.S_IFDIR and recurse:
                        visit.append(fp)
        l.sort()
        return l

    def datafiles(self, matcher=None):
        return self._walk('data', True) + self._walk('meta', True)

    def topfiles(self):
        # yield manifest before changelog
        return reversed(self._walk('', False))

    def walk(self, matcher=None):
        '''yields (unencoded, encoded, size)

        if a matcher is passed, storage files of only those tracked paths
        are passed with matches the matcher
        '''
        # yield data files first
        for x in self.datafiles(matcher):
            yield x
        for x in self.topfiles():
            yield x

    def copylist(self):
        return ['requires'] + _data.split()

    def write(self, tr):
        pass

    def invalidatecaches(self):
        pass

    def markremoved(self, fn):
        pass

    def __contains__(self, path):
        '''Checks if the store contains path'''
        path = "/".join(("data", path))
        # file?
        if self.vfs.exists(path + ".i"):
            return True
        # dir?
        if not path.endswith("/"):
            path = path + "/"
        return self.vfs.exists(path)

class encodedstore(basicstore):
    def __init__(self, path, vfstype):
        vfs = vfstype(path + '/store')
        self.path = vfs.base
        self.createmode = _calcmode(vfs)
        vfs.createmode = self.createmode
        self.rawvfs = vfs
        self.vfs = vfsmod.filtervfs(vfs, encodefilename)
        self.opener = self.vfs

    def datafiles(self, matcher=None):
        for a, b, size in super(encodedstore, self).datafiles():
            try:
                a = decodefilename(a)
            except KeyError:
                a = None
            if a is not None and not _matchtrackedpath(a, matcher):
                continue
            yield a, b, size

    def join(self, f):
        return self.path + '/' + encodefilename(f)

    def copylist(self):
        return (['requires', '00changelog.i'] +
                ['store/' + f for f in _data.split()])

class fncache(object):
    # the filename used to be partially encoded
    # hence the encodedir/decodedir dance
    def __init__(self, vfs):
        self.vfs = vfs
        self.entries = None
        self._dirty = False
        # set of new additions to fncache
        self.addls = set()

    def ensureloaded(self, warn=None):
        '''read the fncache file if not already read.

        If the file on disk is corrupted, raise. If warn is provided,
        warn and keep going instead.'''
        if self.entries is None:
            self._load(warn)

    def _load(self, warn=None):
        '''fill the entries from the fncache file'''
        self._dirty = False
        try:
            fp = self.vfs('fncache', mode='rb')
        except IOError:
            # skip nonexistent file
            self.entries = set()
            return

        self.entries = set()
        chunk = b''
        for c in iter(functools.partial(fp.read, fncache_chunksize), b''):
            chunk += c
            try:
                p = chunk.rindex(b'\n')
                self.entries.update(decodedir(chunk[:p + 1]).splitlines())
                chunk = chunk[p + 1:]
            except ValueError:
                # substring '\n' not found, maybe the entry is bigger than the
                # chunksize, so let's keep iterating
                pass

        if chunk:
            msg = _("fncache does not ends with a newline")
            if warn:
                warn(msg + '\n')
            else:
                raise error.Abort(msg,
                                  hint=_("use 'hg debugrebuildfncache' to "
                                         "rebuild the fncache"))
        self._checkentries(fp, warn)
        fp.close()

    def _checkentries(self, fp, warn):
        """ make sure there is no empty string in entries """
        if '' in self.entries:
            fp.seek(0)
            for n, line in enumerate(util.iterfile(fp)):
                if not line.rstrip('\n'):
                    t = _('invalid entry in fncache, line %d') % (n + 1)
                    if warn:
                        warn(t + '\n')
                    else:
                        raise error.Abort(t)

    def write(self, tr):
        if self._dirty:
            assert self.entries is not None
            self.entries = self.entries | self.addls
            self.addls = set()
            tr.addbackup('fncache')
            fp = self.vfs('fncache', mode='wb', atomictemp=True)
            if self.entries:
                fp.write(encodedir('\n'.join(self.entries) + '\n'))
            fp.close()
            self._dirty = False
        if self.addls:
            # if we have just new entries, let's append them to the fncache
            tr.addbackup('fncache')
            fp = self.vfs('fncache', mode='ab', atomictemp=True)
            if self.addls:
                fp.write(encodedir('\n'.join(self.addls) + '\n'))
            fp.close()
            self.entries = None
            self.addls = set()

    def add(self, fn):
        if self.entries is None:
            self._load()
        if fn not in self.entries:
            self.addls.add(fn)

    def remove(self, fn):
        if self.entries is None:
            self._load()
        if fn in self.addls:
            self.addls.remove(fn)
            return
        try:
            self.entries.remove(fn)
            self._dirty = True
        except KeyError:
            pass

    def __contains__(self, fn):
        if fn in self.addls:
            return True
        if self.entries is None:
            self._load()
        return fn in self.entries

    def __iter__(self):
        if self.entries is None:
            self._load()
        return iter(self.entries | self.addls)

class _fncachevfs(vfsmod.proxyvfs):
    def __init__(self, vfs, fnc, encode):
        vfsmod.proxyvfs.__init__(self, vfs)
        self.fncache = fnc
        self.encode = encode

    def __call__(self, path, mode='r', *args, **kw):
        encoded = self.encode(path)
        if mode not in ('r', 'rb') and (path.startswith('data/') or
                                        path.startswith('meta/')):
            # do not trigger a fncache load when adding a file that already is
            # known to exist.
            notload = self.fncache.entries is None and self.vfs.exists(encoded)
            if notload and 'a' in mode and not self.vfs.stat(encoded).st_size:
                # when appending to an existing file, if the file has size zero,
                # it should be considered as missing. Such zero-size files are
                # the result of truncation when a transaction is aborted.
                notload = False
            if not notload:
                self.fncache.add(path)
        return self.vfs(encoded, mode, *args, **kw)

    def join(self, path):
        if path:
            return self.vfs.join(self.encode(path))
        else:
            return self.vfs.join(path)

class fncachestore(basicstore):
    def __init__(self, path, vfstype, dotencode):
        if dotencode:
            encode = _pathencode
        else:
            encode = _plainhybridencode
        self.encode = encode
        vfs = vfstype(path + '/store')
        self.path = vfs.base
        self.pathsep = self.path + '/'
        self.createmode = _calcmode(vfs)
        vfs.createmode = self.createmode
        self.rawvfs = vfs
        fnc = fncache(vfs)
        self.fncache = fnc
        self.vfs = _fncachevfs(vfs, fnc, encode)
        self.opener = self.vfs

    def join(self, f):
        return self.pathsep + self.encode(f)

    def getsize(self, path):
        return self.rawvfs.stat(path).st_size

    def datafiles(self, matcher=None):
        for f in sorted(self.fncache):
            if not _matchtrackedpath(f, matcher):
                continue
            ef = self.encode(f)
            try:
                yield f, ef, self.getsize(ef)
            except OSError as err:
                if err.errno != errno.ENOENT:
                    raise

    def copylist(self):
        d = ('bookmarks narrowspec data meta dh fncache phaseroots obsstore'
             ' 00manifest.d 00manifest.i 00changelog.d 00changelog.i')
        return (['requires', '00changelog.i'] +
                ['store/' + f for f in d.split()])

    def write(self, tr):
        self.fncache.write(tr)

    def invalidatecaches(self):
        self.fncache.entries = None
        self.fncache.addls = set()

    def markremoved(self, fn):
        self.fncache.remove(fn)

    def _exists(self, f):
        ef = self.encode(f)
        try:
            self.getsize(ef)
            return True
        except OSError as err:
            if err.errno != errno.ENOENT:
                raise
            # nonexistent entry
            return False

    def __contains__(self, path):
        '''Checks if the store contains path'''
        path = "/".join(("data", path))
        # check for files (exact match)
        e = path + '.i'
        if e in self.fncache and self._exists(e):
            return True
        # now check for directories (prefix match)
        if not path.endswith('/'):
            path += '/'
        for e in self.fncache:
            if e.startswith(path) and self._exists(e):
                return True
        return False