sparse-revlog: implement algorithm to write sparse delta chains (
issue5480)
The classic behavior of revlog._isgooddeltainfo is to consider the span size
of the whole delta chain, and limit it to 4 * textlen.
Once sparse-revlog writing is allowed (and enforced with a requirement),
revlog._isgooddeltainfo considers the span of the largest chunk as the
distance used in the verification, instead of using the span of the whole
delta chain.
In order to compute the span of the largest chunk, we need to slice into
chunks a chain with the new revision at the top of the revlog, and take the
maximal span of these chunks. The sparse read density is a parameter to the
slicing, as it will stop when the global read density reaches this threshold.
For instance, a density of 50% means that 2 of 4 read bytes are actually used
for the reconstruction of the revision (the others are part of other chains).
This allows a new revision to be potentially stored with a diff against
another revision anywhere in the history, instead of forcing it in the last 4
* textlen. The result is a much better compression on repositories that have
many concurrent branches. Here are a comparison between using deltas from
current upstream (aggressive-merge-deltas on by default) and deltas from a
sparse-revlog
Comparison of `.hg/store/` size:
mercurial (6.74% merges):
before: 46,831,873 bytes
after: 46,795,992 bytes (no relevant change)
pypy (8.30% merges):
before: 333,524,651 bytes
after: 308,417,511 bytes -8%
netbeans (34.21% merges):
before: 1,141,847,554 bytes
after: 1,131,093,161 bytes -1%
mozilla-central (4.84% merges):
before: 2,344,248,850 bytes
after: 2,328,459,258 bytes -1%
large-private-repo-A (merge 19.73%)
before: 41,510,550,163 bytes
after: 8,121,763,428 bytes -80%
large-private-repo-B (23.77%)
before: 58,702,221,709 bytes
after: 8,351,588,828 bytes -76%
Comparison of `00manifest.d` size:
mercurial (6.74% merges):
before: 6,143,044 bytes
after: 6,107,163 bytes
pypy (8.30% merges):
before: 52,941,780 bytes
after: 27,834,082 bytes -48%
netbeans (34.21% merges):
before: 130,088,982 bytes
after: 119,337,636 bytes -10%
mozilla-central (4.84% merges):
before: 215,096,339 bytes
after: 199,496,863 bytes -8%
large-private-repo-A (merge 19.73%)
before: 33,725,285,081 bytes
after: 390,302,545 bytes -99%
large-private-repo-B (23.77%)
before: 49,457,701,645 bytes
after: 1,366,752,187 bytes -97%
The better delta chains provide a performance boost in relevant repositories:
pypy, bundling 1000 revisions:
before: 1.670s
after: 1.149s -31%
Unbundling got a bit slower. probably because the sparse algorithm is still
pure
python.
pypy, unbundling 1000 revisions:
before: 4.062s
after: 4.507s +10%
Performance of bundle/unbundle in repository with few concurrent branches (eg:
mercurial) are unaffected.
No significant differences have been noticed then timing `hg push` and `hg
pull` locally. More state timings are being gathered.
Same as for aggressive-merge-delta, better delta comes with longer delta
chains. Longer chains have a performance impact. For example. The length of
the chain needed to get the manifest of pypy's tip moves from 82 item to 1929
items. This moves the restore time from 3.88ms to 11.3ms.
Delta chain length is an independent issue that affects repository without
this changes. It will be dealt with independently.
No significant differences have been observed on repositories where
`sparse-revlog` have not much effect (mercurial, unity, netbeans). On pypy,
small differences have been observed on some operation affected by delta chain
building and retrieval.
pypy, perfmanifest
before: 0.006162s
after: 0.017899s +190%
pypy, commit:
before: 0.382
after: 0.376 -1%
pypy, status:
before: 0.157
after: 0.168 +7%
More comprehensive and stable timing comparisons are in progress.
# Copyright (C) 2006 - Marco Barisione <marco@barisione.org>
#
# This is a small extension for Mercurial (https://mercurial-scm.org/)
# that removes files not known to mercurial
#
# This program was inspired by the "cvspurge" script contained in CVS
# utilities (http://www.red-bean.com/cvsutils/).
#
# For help on the usage of "hg purge" use:
# hg help purge
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, see <http://www.gnu.org/licenses/>.
'''command to delete untracked files from the working directory'''
from __future__ import absolute_import
import os
from mercurial.i18n import _
from mercurial import (
cmdutil,
error,
pycompat,
registrar,
scmutil,
util,
)
cmdtable = {}
command = registrar.command(cmdtable)
# Note for extension authors: ONLY specify testedwith = 'ships-with-hg-core' for
# extensions which SHIP WITH MERCURIAL. Non-mainline extensions should
# be specifying the version(s) of Mercurial they are tested with, or
# leave the attribute unspecified.
testedwith = 'ships-with-hg-core'
@command('purge|clean',
[('a', 'abort-on-err', None, _('abort if an error occurs')),
('', 'all', None, _('purge ignored files too')),
('', 'dirs', None, _('purge empty directories')),
('', 'files', None, _('purge files')),
('p', 'print', None, _('print filenames instead of deleting them')),
('0', 'print0', None, _('end filenames with NUL, for use with xargs'
' (implies -p/--print)')),
] + cmdutil.walkopts,
_('hg purge [OPTION]... [DIR]...'))
def purge(ui, repo, *dirs, **opts):
'''removes files not tracked by Mercurial
Delete files not known to Mercurial. This is useful to test local
and uncommitted changes in an otherwise-clean source tree.
This means that purge will delete the following by default:
- Unknown files: files marked with "?" by :hg:`status`
- Empty directories: in fact Mercurial ignores directories unless
they contain files under source control management
But it will leave untouched:
- Modified and unmodified tracked files
- Ignored files (unless --all is specified)
- New files added to the repository (with :hg:`add`)
The --files and --dirs options can be used to direct purge to delete
only files, only directories, or both. If neither option is given,
both will be deleted.
If directories are given on the command line, only files in these
directories are considered.
Be careful with purge, as you could irreversibly delete some files
you forgot to add to the repository. If you only want to print the
list of files that this program would delete, use the --print
option.
'''
opts = pycompat.byteskwargs(opts)
act = not opts.get('print')
eol = '\n'
if opts.get('print0'):
eol = '\0'
act = False # --print0 implies --print
removefiles = opts.get('files')
removedirs = opts.get('dirs')
if not removefiles and not removedirs:
removefiles = True
removedirs = True
def remove(remove_func, name):
if act:
try:
remove_func(repo.wjoin(name))
except OSError:
m = _('%s cannot be removed') % name
if opts.get('abort_on_err'):
raise error.Abort(m)
ui.warn(_('warning: %s\n') % m)
else:
ui.write('%s%s' % (name, eol))
match = scmutil.match(repo[None], dirs, opts)
if removedirs:
directories = []
match.explicitdir = match.traversedir = directories.append
status = repo.status(match=match, ignored=opts.get('all'), unknown=True)
if removefiles:
for f in sorted(status.unknown + status.ignored):
if act:
ui.note(_('removing file %s\n') % f)
remove(util.unlink, f)
if removedirs:
for f in sorted(directories, reverse=True):
if match(f) and not os.listdir(repo.wjoin(f)):
if act:
ui.note(_('removing directory %s\n') % f)
remove(os.rmdir, f)