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util: implement zstd compression engine...
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.

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simplemerge
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Alexis S. L. Carvalho
actually port simplemerge to hg...
r4363 #!/usr/bin/env python
Alexis S. L. Carvalho
Import 3-way merge code from bzr...
r4362
Alexis S. L. Carvalho
polish the simplemerge command; add a test
r4364 from mercurial import demandimport
demandimport.enable()
Alexis S. L. Carvalho
Import 3-way merge code from bzr...
r4362
Simon Heimberg
cleanup: drop unused variables and an unused import
r19378 import sys
Alexis S. L. Carvalho
actually port simplemerge to hg...
r4363 from mercurial.i18n import _
Pierre-Yves David
error: get Abort from 'error' instead of 'util'...
r26587 from mercurial import error, simplemerge, fancyopts, util, ui
Alexis S. L. Carvalho
Import 3-way merge code from bzr...
r4362
Alexis S. L. Carvalho
polish the simplemerge command; add a test
r4364 options = [('L', 'label', [], _('labels to use on conflict markers')),
('a', 'text', None, _('treat all files as text')),
('p', 'print', None,
_('print results instead of overwriting LOCAL')),
Pierre-Yves David
simplemerge: burn "minimal" feature to the ground...
r22023 ('', 'no-minimal', None, _('no effect (DEPRECATED)')),
Alexis S. L. Carvalho
polish the simplemerge command; add a test
r4364 ('h', 'help', None, _('display help and exit')),
('q', 'quiet', None, _('suppress output'))]
usage = _('''simplemerge [OPTS] LOCAL BASE OTHER
Simple three-way file merge utility with a minimal feature set.
Thomas Arendsen Hein
Remove trailing spaces
r5081
Alexis S. L. Carvalho
polish the simplemerge command; add a test
r4364 Apply to LOCAL the changes necessary to go from BASE to OTHER.
Thomas Arendsen Hein
Remove trailing spaces
r5081
Alexis S. L. Carvalho
polish the simplemerge command; add a test
r4364 By default, LOCAL is overwritten with the results of this operation.
''')
Matt Mackall
merge: move the bulk of simplemerge into core...
r6002 class ParseError(Exception):
"""Exception raised on errors in parsing the command line."""
Alexis S. L. Carvalho
polish the simplemerge command; add a test
r4364 def showhelp():
sys.stdout.write(usage)
sys.stdout.write('\noptions:\n')
Alexis S. L. Carvalho
Import 3-way merge code from bzr...
r4362
Alexis S. L. Carvalho
polish the simplemerge command; add a test
r4364 out_opts = []
for shortopt, longopt, default, desc in options:
out_opts.append(('%2s%s' % (shortopt and '-%s' % shortopt,
longopt and ' --%s' % longopt),
'%s' % desc))
opts_len = max([len(opt[0]) for opt in out_opts])
for first, second in out_opts:
sys.stdout.write(' %-*s %s\n' % (opts_len, first, second))
Matt Mackall
merge: move the bulk of simplemerge into core...
r6002 try:
Patrick Mezard
tests: Windows compatibility fixes...
r7080 for fp in (sys.stdin, sys.stdout, sys.stderr):
Adrian Buehlmann
rename util.set_binary to setbinary
r14233 util.setbinary(fp)
Mads Kiilerich
tests: run check-code on Python files without .py extension
r19022
Matt Mackall
merge: move the bulk of simplemerge into core...
r6002 opts = {}
Alexis S. L. Carvalho
polish the simplemerge command; add a test
r4364 try:
Matt Mackall
merge: move the bulk of simplemerge into core...
r6002 args = fancyopts.fancyopts(sys.argv[1:], options, opts)
FUJIWARA Katsunori
misc: use modern exception syntax...
r28047 except fancyopts.getopt.GetoptError as e:
Matt Mackall
merge: move the bulk of simplemerge into core...
r6002 raise ParseError(e)
if opts['help']:
Alexis S. L. Carvalho
polish the simplemerge command; add a test
r4364 showhelp()
Matt Mackall
merge: move the bulk of simplemerge into core...
r6002 sys.exit(0)
if len(args) != 3:
raise ParseError(_('wrong number of arguments'))
Steve Borho
simplemerge: use ui.warn() for warnings
r8269 sys.exit(simplemerge.simplemerge(ui.ui(), *args, **opts))
FUJIWARA Katsunori
misc: use modern exception syntax...
r28047 except ParseError as e:
Matt Mackall
merge: move the bulk of simplemerge into core...
r6002 sys.stdout.write("%s: %s\n" % (sys.argv[0], e))
showhelp()
sys.exit(1)
FUJIWARA Katsunori
misc: use modern exception syntax...
r28047 except error.Abort as e:
Matt Mackall
merge: move the bulk of simplemerge into core...
r6002 sys.stderr.write("abort: %s\n" % e)
sys.exit(255)
except KeyboardInterrupt:
sys.exit(255)