view hgext/convert/bzr.py @ 30212:260af19891f2

changegroup: increase write buffer size to 128k

By default, Python defers to the operating system for choosing the
default buffer size on opened files. On my Linux machine, the default
is 4k, which is really small for 2016.

This patch bumps the write buffer size when writing
changegroups/bundles to 128k. This matches the 128k read buffer
we already use on revlogs.

It's worth noting that this only impacts when writing to an explicit
file (such as during `hg bundle`). Buffers when writing to bundle
files via the repo vfs or to a temporary file are not impacted.

When producing a none-v2 bundle file of the mozilla-unified repository,
this change caused the number of write() system calls to drop from
952,449 to 29,788. After this change, the most frequent system
calls are fstat(), read(), lseek(), and open(). There were
2,523,672 system calls after this patch (so a net decrease of
~950k is statistically significant).

This change shows no performance change on my system. But I have a
high-end system with a fast SSD. It is quite possible this change
will have a significant impact on network file systems, where
extra network round trips due to excessive I/O system calls could
introduce significant latency.

# bzr.py - bzr support for the convert extension
#
#  Copyright 2008, 2009 Marek Kubica <[e-mail]> and others
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

# This module is for handling 'bzr', that was formerly known as Bazaar-NG;
# it cannot access 'bar' repositories, but they were never used very much
from __future__ import absolute_import

import os

from mercurial.i18n import _
from mercurial import (
    demandimport,
    error
)
from . import common

# these do not work with demandimport, blacklist
demandimport.ignore.extend([
        'bzrlib.transactions',
        'bzrlib.urlutils',
        'ElementPath',
    ])

try:
    # bazaar imports
    import bzrlib.bzrdir
    import bzrlib.errors
    import bzrlib.revision
    import bzrlib.revisionspec.RevisionSpec
    bzrdir = bzrlib.bzrdir
    errors = bzrlib.errors
    revision = bzrlib.revision
    revisionspec = bzrlib.revisionspec
except ImportError:
    pass

supportedkinds = ('file', 'symlink')

class bzr_source(common.converter_source):
    """Reads Bazaar repositories by using the Bazaar Python libraries"""

    def __init__(self, ui, path, revs=None):
        super(bzr_source, self).__init__(ui, path, revs=revs)

        if not os.path.exists(os.path.join(path, '.bzr')):
            raise common.NoRepo(_('%s does not look like a Bazaar repository')
                              % path)

        try:
            # access bzrlib stuff
            bzrdir
        except NameError:
            raise common.NoRepo(_('Bazaar modules could not be loaded'))

        path = os.path.abspath(path)
        self._checkrepotype(path)
        try:
            self.sourcerepo = bzrdir.BzrDir.open(path).open_repository()
        except errors.NoRepositoryPresent:
            raise common.NoRepo(_('%s does not look like a Bazaar repository')
                              % path)
        self._parentids = {}

    def _checkrepotype(self, path):
        # Lightweight checkouts detection is informational but probably
        # fragile at API level. It should not terminate the conversion.
        try:
            dir = bzrdir.BzrDir.open_containing(path)[0]
            try:
                tree = dir.open_workingtree(recommend_upgrade=False)
                branch = tree.branch
            except (errors.NoWorkingTree, errors.NotLocalUrl):
                tree = None
                branch = dir.open_branch()
            if (tree is not None and tree.bzrdir.root_transport.base !=
                branch.bzrdir.root_transport.base):
                self.ui.warn(_('warning: lightweight checkouts may cause '
                               'conversion failures, try with a regular '
                               'branch instead.\n'))
        except Exception:
            self.ui.note(_('bzr source type could not be determined\n'))

    def before(self):
        """Before the conversion begins, acquire a read lock
        for all the operations that might need it. Fortunately
        read locks don't block other reads or writes to the
        repository, so this shouldn't have any impact on the usage of
        the source repository.

        The alternative would be locking on every operation that
        needs locks (there are currently two: getting the file and
        getting the parent map) and releasing immediately after,
        but this approach can take even 40% longer."""
        self.sourcerepo.lock_read()

    def after(self):
        self.sourcerepo.unlock()

    def _bzrbranches(self):
        return self.sourcerepo.find_branches(using=True)

    def getheads(self):
        if not self.revs:
            # Set using=True to avoid nested repositories (see issue3254)
            heads = sorted([b.last_revision() for b in self._bzrbranches()])
        else:
            revid = None
            for branch in self._bzrbranches():
                try:
                    r = revisionspec.RevisionSpec.from_string(self.revs[0])
                    info = r.in_history(branch)
                except errors.BzrError:
                    pass
                revid = info.rev_id
            if revid is None:
                raise error.Abort(_('%s is not a valid revision')
                                  % self.revs[0])
            heads = [revid]
        # Empty repositories return 'null:', which cannot be retrieved
        heads = [h for h in heads if h != 'null:']
        return heads

    def getfile(self, name, rev):
        revtree = self.sourcerepo.revision_tree(rev)
        fileid = revtree.path2id(name.decode(self.encoding or 'utf-8'))
        kind = None
        if fileid is not None:
            kind = revtree.kind(fileid)
        if kind not in supportedkinds:
            # the file is not available anymore - was deleted
            return None, None
        mode = self._modecache[(name, rev)]
        if kind == 'symlink':
            target = revtree.get_symlink_target(fileid)
            if target is None:
                raise error.Abort(_('%s.%s symlink has no target')
                                 % (name, rev))
            return target, mode
        else:
            sio = revtree.get_file(fileid)
            return sio.read(), mode

    def getchanges(self, version, full):
        if full:
            raise error.Abort(_("convert from cvs does not support --full"))
        self._modecache = {}
        self._revtree = self.sourcerepo.revision_tree(version)
        # get the parentids from the cache
        parentids = self._parentids.pop(version)
        # only diff against first parent id
        prevtree = self.sourcerepo.revision_tree(parentids[0])
        files, changes = self._gettreechanges(self._revtree, prevtree)
        return files, changes, set()

    def getcommit(self, version):
        rev = self.sourcerepo.get_revision(version)
        # populate parent id cache
        if not rev.parent_ids:
            parents = []
            self._parentids[version] = (revision.NULL_REVISION,)
        else:
            parents = self._filterghosts(rev.parent_ids)
            self._parentids[version] = parents

        branch = self.recode(rev.properties.get('branch-nick', u'default'))
        if branch == 'trunk':
            branch = 'default'
        return common.commit(parents=parents,
                date='%d %d' % (rev.timestamp, -rev.timezone),
                author=self.recode(rev.committer),
                desc=self.recode(rev.message),
                branch=branch,
                rev=version)

    def gettags(self):
        bytetags = {}
        for branch in self._bzrbranches():
            if not branch.supports_tags():
                return {}
            tagdict = branch.tags.get_tag_dict()
            for name, rev in tagdict.iteritems():
                bytetags[self.recode(name)] = rev
        return bytetags

    def getchangedfiles(self, rev, i):
        self._modecache = {}
        curtree = self.sourcerepo.revision_tree(rev)
        if i is not None:
            parentid = self._parentids[rev][i]
        else:
            # no parent id, get the empty revision
            parentid = revision.NULL_REVISION

        prevtree = self.sourcerepo.revision_tree(parentid)
        changes = [e[0] for e in self._gettreechanges(curtree, prevtree)[0]]
        return changes

    def _gettreechanges(self, current, origin):
        revid = current._revision_id
        changes = []
        renames = {}
        seen = set()
        # Process the entries by reverse lexicographic name order to
        # handle nested renames correctly, most specific first.
        curchanges = sorted(current.iter_changes(origin),
                            key=lambda c: c[1][0] or c[1][1],
                            reverse=True)
        for (fileid, paths, changed_content, versioned, parent, name,
            kind, executable) in curchanges:

            if paths[0] == u'' or paths[1] == u'':
                # ignore changes to tree root
                continue

            # bazaar tracks directories, mercurial does not, so
            # we have to rename the directory contents
            if kind[1] == 'directory':
                if kind[0] not in (None, 'directory'):
                    # Replacing 'something' with a directory, record it
                    # so it can be removed.
                    changes.append((self.recode(paths[0]), revid))

                if kind[0] == 'directory' and None not in paths:
                    renaming = paths[0] != paths[1]
                    # neither an add nor an delete - a move
                    # rename all directory contents manually
                    subdir = origin.root_inventory.path2id(paths[0])
                    # get all child-entries of the directory
                    for name, entry in origin.root_inventory.iter_entries(
                            subdir):
                        # hg does not track directory renames
                        if entry.kind == 'directory':
                            continue
                        frompath = self.recode(paths[0] + '/' + name)
                        if frompath in seen:
                            # Already handled by a more specific change entry
                            # This is important when you have:
                            # a => b
                            # a/c => a/c
                            # Here a/c must not be renamed into b/c
                            continue
                        seen.add(frompath)
                        if not renaming:
                            continue
                        topath = self.recode(paths[1] + '/' + name)
                        # register the files as changed
                        changes.append((frompath, revid))
                        changes.append((topath, revid))
                        # add to mode cache
                        mode = ((entry.executable and 'x')
                                or (entry.kind == 'symlink' and 's')
                                or '')
                        self._modecache[(topath, revid)] = mode
                        # register the change as move
                        renames[topath] = frompath

                # no further changes, go to the next change
                continue

            # we got unicode paths, need to convert them
            path, topath = paths
            if path is not None:
                path = self.recode(path)
            if topath is not None:
                topath = self.recode(topath)
            seen.add(path or topath)

            if topath is None:
                # file deleted
                changes.append((path, revid))
                continue

            # renamed
            if path and path != topath:
                renames[topath] = path
                changes.append((path, revid))

            # populate the mode cache
            kind, executable = [e[1] for e in (kind, executable)]
            mode = ((executable and 'x') or (kind == 'symlink' and 'l')
                    or '')
            self._modecache[(topath, revid)] = mode
            changes.append((topath, revid))

        return changes, renames

    def _filterghosts(self, ids):
        """Filters out ghost revisions which hg does not support, see
        <http://bazaar-vcs.org/GhostRevision>
        """
        parentmap = self.sourcerepo.get_parent_map(ids)
        parents = tuple([parent for parent in ids if parent in parentmap])
        return parents