Mercurial > hg
view mercurial/archival.py @ 30442:41a8106789ca
util: implement zstd compression engine
Now that zstd is vendored and being built (in some configurations), we
can implement a compression engine for zstd!
The zstd engine is a little different from existing engines. Because
it may not always be present, we have to defer load the module in case
importing it fails. We facilitate this via a cached property that holds
a reference to the module or None. The "available" method is
implemented to reflect reality.
The zstd engine declares its ability to handle bundles using the
"zstd" human name and the "ZS" internal name. The latter was chosen
because internal names are 2 characters (by only convention I think)
and "ZS" seems reasonable.
The engine, like others, supports specifying the compression level.
However, there are no consumers of this API that yet pass in that
argument. I have plans to change that, so stay tuned.
Since all we need to do to support bundle generation with a new
compression engine is implement and register the compression engine,
bundle generation with zstd "just works!" Tests demonstrating this
have been added.
How does performance of zstd for bundle generation compare? On the
mozilla-unified repo, `hg bundle --all -t <engine>-v2` yields the
following on my i7-6700K on Linux:
engine CPU time bundle size vs orig size throughput
none 97.0s 4,054,405,584 100.0% 41.8 MB/s
bzip2 (l=9) 393.6s 975,343,098 24.0% 10.3 MB/s
gzip (l=6) 184.0s 1,140,533,074 28.1% 22.0 MB/s
zstd (l=1) 108.2s 1,119,434,718 27.6% 37.5 MB/s
zstd (l=2) 111.3s 1,078,328,002 26.6% 36.4 MB/s
zstd (l=3) 113.7s 1,011,823,727 25.0% 35.7 MB/s
zstd (l=4) 116.0s 1,008,965,888 24.9% 35.0 MB/s
zstd (l=5) 121.0s 977,203,148 24.1% 33.5 MB/s
zstd (l=6) 131.7s 927,360,198 22.9% 30.8 MB/s
zstd (l=7) 139.0s 912,808,505 22.5% 29.2 MB/s
zstd (l=12) 198.1s 854,527,714 21.1% 20.5 MB/s
zstd (l=18) 681.6s 789,750,690 19.5% 5.9 MB/s
On compression, zstd for bundle generation delivers:
* better compression than gzip with significantly less CPU utilization
* better than bzip2 compression ratios while still being significantly
faster than gzip
* ability to aggressively tune compression level to achieve
significantly smaller bundles
That last point is important. With clone bundles, a server can
pre-generate a bundle file, upload it to a static file server, and
redirect clients to transparently download it during clone. The server
could choose to produce a zstd bundle with the highest compression
settings possible. This would take a very long time - a magnitude
longer than a typical zstd bundle generation - but the result would
be hundreds of megabytes smaller! For the clone volume we do at
Mozilla, this could translate to petabytes of bandwidth savings
per year and faster clones (due to smaller transfer size).
I don't have detailed numbers to report on decompression. However,
zstd decompression is fast: >1 GB/s output throughput on this machine,
even through the Python bindings. And it can do that regardless of the
compression level of the input. By the time you have enough data to
worry about overhead of decompression, you have plenty of other things
to worry about performance wise.
zstd is wins all around. I can't wait to implement support for it
on the wire protocol and in revlogs.
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Fri, 11 Nov 2016 01:10:07 -0800 |
parents | 31a6d5e14508 |
children | 798bcb1274dd |
line wrap: on
line source
# archival.py - revision archival for mercurial # # Copyright 2006 Vadim Gelfer <vadim.gelfer@gmail.com> # # 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 gzip import os import struct import tarfile import time import zipfile import zlib from .i18n import _ from . import ( cmdutil, encoding, error, match as matchmod, scmutil, util, ) stringio = util.stringio # from unzip source code: _UNX_IFREG = 0x8000 _UNX_IFLNK = 0xa000 def tidyprefix(dest, kind, prefix): '''choose prefix to use for names in archive. make sure prefix is safe for consumers.''' if prefix: prefix = util.normpath(prefix) else: if not isinstance(dest, str): raise ValueError('dest must be string if no prefix') prefix = os.path.basename(dest) lower = prefix.lower() for sfx in exts.get(kind, []): if lower.endswith(sfx): prefix = prefix[:-len(sfx)] break lpfx = os.path.normpath(util.localpath(prefix)) prefix = util.pconvert(lpfx) if not prefix.endswith('/'): prefix += '/' # Drop the leading '.' path component if present, so Windows can read the # zip files (issue4634) if prefix.startswith('./'): prefix = prefix[2:] if prefix.startswith('../') or os.path.isabs(lpfx) or '/../' in prefix: raise error.Abort(_('archive prefix contains illegal components')) return prefix exts = { 'tar': ['.tar'], 'tbz2': ['.tbz2', '.tar.bz2'], 'tgz': ['.tgz', '.tar.gz'], 'zip': ['.zip'], } def guesskind(dest): for kind, extensions in exts.iteritems(): if any(dest.endswith(ext) for ext in extensions): return kind return None def _rootctx(repo): # repo[0] may be hidden for rev in repo: return repo[rev] return repo['null'] def buildmetadata(ctx): '''build content of .hg_archival.txt''' repo = ctx.repo() hex = ctx.hex() if ctx.rev() is None: hex = ctx.p1().hex() if ctx.dirty(): hex += '+' base = 'repo: %s\nnode: %s\nbranch: %s\n' % ( _rootctx(repo).hex(), hex, encoding.fromlocal(ctx.branch())) tags = ''.join('tag: %s\n' % t for t in ctx.tags() if repo.tagtype(t) == 'global') if not tags: repo.ui.pushbuffer() opts = {'template': '{latesttag}\n{latesttagdistance}\n' '{changessincelatesttag}', 'style': '', 'patch': None, 'git': None} cmdutil.show_changeset(repo.ui, repo, opts).show(ctx) ltags, dist, changessince = repo.ui.popbuffer().split('\n') ltags = ltags.split(':') tags = ''.join('latesttag: %s\n' % t for t in ltags) tags += 'latesttagdistance: %s\n' % dist tags += 'changessincelatesttag: %s\n' % changessince return base + tags class tarit(object): '''write archive to tar file or stream. can write uncompressed, or compress with gzip or bzip2.''' class GzipFileWithTime(gzip.GzipFile): def __init__(self, *args, **kw): timestamp = None if 'timestamp' in kw: timestamp = kw.pop('timestamp') if timestamp is None: self.timestamp = time.time() else: self.timestamp = timestamp gzip.GzipFile.__init__(self, *args, **kw) def _write_gzip_header(self): self.fileobj.write('\037\213') # magic header self.fileobj.write('\010') # compression method fname = self.name if fname and fname.endswith('.gz'): fname = fname[:-3] flags = 0 if fname: flags = gzip.FNAME self.fileobj.write(chr(flags)) gzip.write32u(self.fileobj, long(self.timestamp)) self.fileobj.write('\002') self.fileobj.write('\377') if fname: self.fileobj.write(fname + '\000') def __init__(self, dest, mtime, kind=''): self.mtime = mtime self.fileobj = None def taropen(name, mode, fileobj=None): if kind == 'gz': mode = mode[0] if not fileobj: fileobj = open(name, mode + 'b') gzfileobj = self.GzipFileWithTime(name, mode + 'b', zlib.Z_BEST_COMPRESSION, fileobj, timestamp=mtime) self.fileobj = gzfileobj return tarfile.TarFile.taropen(name, mode, gzfileobj) else: return tarfile.open(name, mode + kind, fileobj) if isinstance(dest, str): self.z = taropen(dest, mode='w:') else: # Python 2.5-2.5.1 have a regression that requires a name arg self.z = taropen(name='', mode='w|', fileobj=dest) def addfile(self, name, mode, islink, data): i = tarfile.TarInfo(name) i.mtime = self.mtime i.size = len(data) if islink: i.type = tarfile.SYMTYPE i.mode = 0o777 i.linkname = data data = None i.size = 0 else: i.mode = mode data = stringio(data) self.z.addfile(i, data) def done(self): self.z.close() if self.fileobj: self.fileobj.close() class tellable(object): '''provide tell method for zipfile.ZipFile when writing to http response file object.''' def __init__(self, fp): self.fp = fp self.offset = 0 def __getattr__(self, key): return getattr(self.fp, key) def write(self, s): self.fp.write(s) self.offset += len(s) def tell(self): return self.offset class zipit(object): '''write archive to zip file or stream. can write uncompressed, or compressed with deflate.''' def __init__(self, dest, mtime, compress=True): if not isinstance(dest, str): try: dest.tell() except (AttributeError, IOError): dest = tellable(dest) self.z = zipfile.ZipFile(dest, 'w', compress and zipfile.ZIP_DEFLATED or zipfile.ZIP_STORED) # Python's zipfile module emits deprecation warnings if we try # to store files with a date before 1980. epoch = 315532800 # calendar.timegm((1980, 1, 1, 0, 0, 0, 1, 1, 0)) if mtime < epoch: mtime = epoch self.mtime = mtime self.date_time = time.gmtime(mtime)[:6] def addfile(self, name, mode, islink, data): i = zipfile.ZipInfo(name, self.date_time) i.compress_type = self.z.compression # unzip will not honor unix file modes unless file creator is # set to unix (id 3). i.create_system = 3 ftype = _UNX_IFREG if islink: mode = 0o777 ftype = _UNX_IFLNK i.external_attr = (mode | ftype) << 16 # add "extended-timestamp" extra block, because zip archives # without this will be extracted with unexpected timestamp, # if TZ is not configured as GMT i.extra += struct.pack('<hhBl', 0x5455, # block type: "extended-timestamp" 1 + 4, # size of this block 1, # "modification time is present" int(self.mtime)) # last modification (UTC) self.z.writestr(i, data) def done(self): self.z.close() class fileit(object): '''write archive as files in directory.''' def __init__(self, name, mtime): self.basedir = name self.opener = scmutil.opener(self.basedir) def addfile(self, name, mode, islink, data): if islink: self.opener.symlink(data, name) return f = self.opener(name, "w", atomictemp=True) f.write(data) f.close() destfile = os.path.join(self.basedir, name) os.chmod(destfile, mode) def done(self): pass archivers = { 'files': fileit, 'tar': tarit, 'tbz2': lambda name, mtime: tarit(name, mtime, 'bz2'), 'tgz': lambda name, mtime: tarit(name, mtime, 'gz'), 'uzip': lambda name, mtime: zipit(name, mtime, False), 'zip': zipit, } def archive(repo, dest, node, kind, decode=True, matchfn=None, prefix='', mtime=None, subrepos=False): '''create archive of repo as it was at node. dest can be name of directory, name of archive file, or file object to write archive to. kind is type of archive to create. decode tells whether to put files through decode filters from hgrc. matchfn is function to filter names of files to write to archive. prefix is name of path to put before every archive member.''' if kind == 'files': if prefix: raise error.Abort(_('cannot give prefix when archiving to files')) else: prefix = tidyprefix(dest, kind, prefix) def write(name, mode, islink, getdata): data = getdata() if decode: data = repo.wwritedata(name, data) archiver.addfile(prefix + name, mode, islink, data) if kind not in archivers: raise error.Abort(_("unknown archive type '%s'") % kind) ctx = repo[node] archiver = archivers[kind](dest, mtime or ctx.date()[0]) if repo.ui.configbool("ui", "archivemeta", True): name = '.hg_archival.txt' if not matchfn or matchfn(name): write(name, 0o644, False, lambda: buildmetadata(ctx)) if matchfn: files = [f for f in ctx.manifest().keys() if matchfn(f)] else: files = ctx.manifest().keys() total = len(files) if total: files.sort() repo.ui.progress(_('archiving'), 0, unit=_('files'), total=total) for i, f in enumerate(files): ff = ctx.flags(f) write(f, 'x' in ff and 0o755 or 0o644, 'l' in ff, ctx[f].data) repo.ui.progress(_('archiving'), i + 1, item=f, unit=_('files'), total=total) repo.ui.progress(_('archiving'), None) if subrepos: for subpath in sorted(ctx.substate): sub = ctx.workingsub(subpath) submatch = matchmod.subdirmatcher(subpath, matchfn) total += sub.archive(archiver, prefix, submatch) if total == 0: raise error.Abort(_('no files match the archive pattern')) archiver.done() return total