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localrepo: experimental support for non-zlib revlog compression...
localrepo: experimental support for non-zlib revlog compression The final part of integrating the compression manager APIs into revlog storage is the plumbing for repositories to advertise they are using non-zlib storage and for revlogs to instantiate a non-zlib compression engine. The main intent of the compression manager work was to zstd all of the things. Adding zstd to revlogs has proved to be more involved than other places because revlogs are... special. Very small inputs and the use of delta chains (which are themselves a form of compression) are a completely different use case from streaming compression, which bundles and the wire protocol employ. I've conducted numerous experiments with zstd in revlogs and have yet to formalize compression settings and a storage architecture that I'm confident I won't regret later. In other words, I'm not yet ready to commit to a new mechanism for using zstd - or any other compression format - in revlogs. That being said, having some support for zstd (and other compression formats) in revlogs in core is beneficial. It can allow others to conduct experiments. This patch introduces *highly experimental* support for non-zlib compression formats in revlogs. Introduced is a config option to control which compression engine to use. Also introduced is a namespace of "exp-compression-*" requirements to denote support for non-zlib compression in revlogs. I've prefixed the namespace with "exp-" (short for "experimental") because I'm not confident of the requirements "schema" and in no way want to give the illusion of supporting these requirements in the future. I fully intend to drop support for these requirements once we figure out what we're doing with zstd in revlogs. A good portion of the patch is teaching the requirements system about registered compression engines and passing the requested compression engine as an opener option so revlogs can instantiate the proper compression engine for new operations. That's a verbose way of saying "we can now use zstd in revlogs!" On an `hg pull` conversion of the mozilla-unified repo with no extra redelta settings (like aggressivemergedeltas), we can see the impact of zstd vs zlib in revlogs: $ hg perfrevlogchunks -c ! chunk ! wall 2.032052 comb 2.040000 user 1.990000 sys 0.050000 (best of 5) ! wall 1.866360 comb 1.860000 user 1.820000 sys 0.040000 (best of 6) ! chunk batch ! wall 1.877261 comb 1.870000 user 1.860000 sys 0.010000 (best of 6) ! wall 1.705410 comb 1.710000 user 1.690000 sys 0.020000 (best of 6) $ hg perfrevlogchunks -m ! chunk ! wall 2.721427 comb 2.720000 user 2.640000 sys 0.080000 (best of 4) ! wall 2.035076 comb 2.030000 user 1.950000 sys 0.080000 (best of 5) ! chunk batch ! wall 2.614561 comb 2.620000 user 2.580000 sys 0.040000 (best of 4) ! wall 1.910252 comb 1.910000 user 1.880000 sys 0.030000 (best of 6) $ hg perfrevlog -c -d 1 ! wall 4.812885 comb 4.820000 user 4.800000 sys 0.020000 (best of 3) ! wall 4.699621 comb 4.710000 user 4.700000 sys 0.010000 (best of 3) $ hg perfrevlog -m -d 1000 ! wall 34.252800 comb 34.250000 user 33.730000 sys 0.520000 (best of 3) ! wall 24.094999 comb 24.090000 user 23.320000 sys 0.770000 (best of 3) Only modest wins for the changelog. But manifest reading is significantly faster. What's going on? One reason might be data volume. zstd decompresses faster. So given more bytes, it will put more distance between it and zlib. Another reason is size. In the current design, zstd revlogs are *larger*: debugcreatestreamclonebundle (size in bytes) zlib: 1,638,852,492 zstd: 1,680,601,332 I haven't investigated this fully, but I reckon a significant cause of larger revlogs is that the zstd frame/header has more bytes than zlib's. For very small inputs or data that doesn't compress well, we'll tend to store more uncompressed chunks than with zlib (because the compressed size isn't smaller than original). This will make revlog reading faster because it is doing less decompression. Moving on to bundle performance: $ hg bundle -a -t none-v2 (total CPU time) zlib: 102.79s zstd: 97.75s So, marginal CPU decrease for reading all chunks in all revlogs (this is somewhat disappointing). $ hg bundle -a -t <engine>-v2 (total CPU time) zlib: 191.59s zstd: 115.36s This last test effectively measures the difference between zlib->zlib and zstd->zstd for revlogs to bundle. This is a rough approximation of what a server does during `hg clone`. There are some promising results for zstd. But not enough for me to feel comfortable advertising it to users. We'll get there...

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patterns.txt
74 lines | 2.8 KiB | text/plain | TextLexer
Dan Villiom Podlaski Christiansen
setup: install translation files as package data...
r9999 Mercurial accepts several notations for identifying one or more files
at a time.
By default, Mercurial treats filenames as shell-style extended glob
patterns.
Alternate pattern notations must be specified explicitly.
FUJIWARA Katsunori
doc: add note about pattern rooted/unrooted cases to "hgignore" and "patterns"...
r16504 .. note::
Simon Heimberg
help: remove last occurrences of ".. note::" without two newlines...
r20532
Mads Kiilerich
check-code: check txt files for trailing whitespace
r18960 Patterns specified in ``.hgignore`` are not rooted.
Mads Kiilerich
docs: don't use :hg: at the beginning of lines in notes (issue3397)...
r16510 Please see :hg:`help hgignore` for details.
FUJIWARA Katsunori
doc: add note about pattern rooted/unrooted cases to "hgignore" and "patterns"...
r16504
Dan Villiom Podlaski Christiansen
setup: install translation files as package data...
r9999 To use a plain path name without any pattern matching, start it with
``path:``. These path names must completely match starting at the
current repository root.
To use an extended glob, start a name with ``glob:``. Globs are rooted
at the current directory; a glob such as ``*.c`` will only match files
in the current directory ending with ``.c``.
The supported glob syntax extensions are ``**`` to match any string
across path separators and ``{a,b}`` to mean "a or b".
To use a Perl/Python regular expression, start a name with ``re:``.
Regexp pattern matching is anchored at the root of the repository.
Steve Borho
match: support reading pattern lists from files
r13218 To read name patterns from a file, use ``listfile:`` or ``listfile0:``.
The latter expects null delimited patterns while the former expects line
feeds. Each string read from the file is itself treated as a file
pattern.
Durham Goode
help: add documentation on include: and subinclude:...
r25284 To read a set of patterns from a file, use ``include:`` or ``subinclude:``.
``include:`` will use all the patterns from the given file and treat them as if
they had been passed in manually. ``subinclude:`` will only apply the patterns
against files that are under the subinclude file's directory. See :hg:`help
hgignore` for details on the format of these files.
FUJIWARA Katsunori
doc: add description about pattern matching against directories...
r20290 All patterns, except for ``glob:`` specified in command line (not for
FUJIWARA Katsunori
doc: fix mistake about matching against directories in "pattern.txt"...
r20329 ``-I`` or ``-X`` options), can match also against directories: files
under matched directories are treated as matched.
FUJIWARA Katsunori
doc: add description about pattern matching against directories...
r20290
Dan Villiom Podlaski Christiansen
setup: install translation files as package data...
r9999 Plain examples::
path:foo/bar a name bar in a directory named foo in the root
of the repository
path:path:name a file or directory named "path:name"
Glob examples::
glob:*.c any name ending in ".c" in the current directory
*.c any name ending in ".c" in the current directory
**.c any name ending in ".c" in any subdirectory of the
current directory including itself.
foo/*.c any name ending in ".c" in the directory foo
foo/**.c any name ending in ".c" in any subdirectory of foo
including itself.
Regexp examples::
re:.*\.c$ any name ending in ".c", anywhere in the repository
Steve Borho
match: support reading pattern lists from files
r13218
File examples::
listfile:list.txt read list from list.txt with one file pattern per line
listfile0:list.txt read list from list.txt with null byte delimiters
Matt Mackall
fileset: add a help topic...
r14686
See also :hg:`help filesets`.
Durham Goode
help: add documentation on include: and subinclude:...
r25284
Include examples::
include:path/to/mypatternfile reads patterns to be applied to all paths
subinclude:path/to/subignorefile reads patterns specifically for paths in the
subdirectory