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...
Show all commands except debug commands
$ hg debugcomplete
add
addremove
annotate
archive
backout
bisect
bookmarks
branch
branches
bundle
cat
clone
commit
config
copy
diff
export
files
forget
graft
grep
heads
help
identify
import
incoming
init
locate
log
manifest
merge
outgoing
parents
paths
phase
pull
push
recover
remove
rename
resolve
revert
rollback
root
serve
status
summary
tag
tags
tip
unbundle
update
verify
version
Show all commands that start with "a"
$ hg debugcomplete a
add
addremove
annotate
archive
Do not show debug commands if there are other candidates
$ hg debugcomplete d
diff
Show debug commands if there are no other candidates
$ hg debugcomplete debug
debugancestor
debugapplystreamclonebundle
debugbuilddag
debugbundle
debugcheckstate
debugcommands
debugcomplete
debugconfig
debugcreatestreamclonebundle
debugdag
debugdata
debugdate
debugdeltachain
debugdirstate
debugdiscovery
debugextensions
debugfileset
debugfsinfo
debuggetbundle
debugignore
debugindex
debugindexdot
debuginstall
debugknown
debuglabelcomplete
debuglocks
debugmergestate
debugnamecomplete
debugobsolete
debugpathcomplete
debugpushkey
debugpvec
debugrebuilddirstate
debugrebuildfncache
debugrename
debugrevlog
debugrevspec
debugsetparents
debugsub
debugsuccessorssets
debugtemplate
debugupgraderepo
debugwalk
debugwireargs
Do not show the alias of a debug command if there are other candidates
(this should hide rawcommit)
$ hg debugcomplete r
recover
remove
rename
resolve
revert
rollback
root
Show the alias of a debug command if there are no other candidates
$ hg debugcomplete rawc
Show the global options
$ hg debugcomplete --options | sort
--config
--cwd
--debug
--debugger
--encoding
--encodingmode
--help
--hidden
--noninteractive
--profile
--quiet
--repository
--time
--traceback
--verbose
--version
-R
-h
-q
-v
-y
Show the options for the "serve" command
$ hg debugcomplete --options serve | sort
--accesslog
--address
--certificate
--cmdserver
--config
--cwd
--daemon
--daemon-postexec
--debug
--debugger
--encoding
--encodingmode
--errorlog
--help
--hidden
--ipv6
--name
--noninteractive
--pid-file
--port
--prefix
--profile
--quiet
--repository
--stdio
--style
--templates
--time
--traceback
--verbose
--version
--web-conf
-6
-A
-E
-R
-a
-d
-h
-n
-p
-q
-t
-v
-y
Show an error if we use --options with an ambiguous abbreviation
$ hg debugcomplete --options s
hg: command 's' is ambiguous:
serve showconfig status summary
[255]
Show all commands + options
$ hg debugcommands
add: include, exclude, subrepos, dry-run
annotate: rev, follow, no-follow, text, user, file, date, number, changeset, line-number, ignore-all-space, ignore-space-change, ignore-blank-lines, include, exclude, template
clone: noupdate, updaterev, rev, branch, pull, uncompressed, ssh, remotecmd, insecure
commit: addremove, close-branch, amend, secret, edit, interactive, include, exclude, message, logfile, date, user, subrepos
diff: rev, change, text, git, nodates, noprefix, show-function, reverse, ignore-all-space, ignore-space-change, ignore-blank-lines, unified, stat, root, include, exclude, subrepos
export: output, switch-parent, rev, text, git, nodates
forget: include, exclude
init: ssh, remotecmd, insecure
log: follow, follow-first, date, copies, keyword, rev, removed, only-merges, user, only-branch, branch, prune, patch, git, limit, no-merges, stat, graph, style, template, include, exclude
merge: force, rev, preview, tool
pull: update, force, rev, bookmark, branch, ssh, remotecmd, insecure
push: force, rev, bookmark, branch, new-branch, ssh, remotecmd, insecure
remove: after, force, subrepos, include, exclude
serve: accesslog, daemon, daemon-postexec, errorlog, port, address, prefix, name, web-conf, webdir-conf, pid-file, stdio, cmdserver, templates, style, ipv6, certificate
status: all, modified, added, removed, deleted, clean, unknown, ignored, no-status, copies, print0, rev, change, include, exclude, subrepos, template
summary: remote
update: clean, check, date, rev, tool
addremove: similarity, subrepos, include, exclude, dry-run
archive: no-decode, prefix, rev, type, subrepos, include, exclude
backout: merge, commit, no-commit, parent, rev, edit, tool, include, exclude, message, logfile, date, user
bisect: reset, good, bad, skip, extend, command, noupdate
bookmarks: force, rev, delete, rename, inactive, template
branch: force, clean
branches: active, closed, template
bundle: force, rev, branch, base, all, type, ssh, remotecmd, insecure
cat: output, rev, decode, include, exclude
config: untrusted, edit, local, global, template
copy: after, force, include, exclude, dry-run
debugancestor:
debugapplystreamclonebundle:
debugbuilddag: mergeable-file, overwritten-file, new-file
debugbundle: all, spec
debugcheckstate:
debugcommands:
debugcomplete: options
debugcreatestreamclonebundle:
debugdag: tags, branches, dots, spaces
debugdata: changelog, manifest, dir
debugdate: extended
debugdeltachain: changelog, manifest, dir, template
debugdirstate: nodates, datesort
debugdiscovery: old, nonheads, ssh, remotecmd, insecure
debugextensions: template
debugfileset: rev
debugfsinfo:
debuggetbundle: head, common, type
debugignore:
debugindex: changelog, manifest, dir, format
debugindexdot: changelog, manifest, dir
debuginstall: template
debugknown:
debuglabelcomplete:
debuglocks: force-lock, force-wlock
debugmergestate:
debugnamecomplete:
debugobsolete: flags, record-parents, rev, index, delete, date, user, template
debugpathcomplete: full, normal, added, removed
debugpushkey:
debugpvec:
debugrebuilddirstate: rev, minimal
debugrebuildfncache:
debugrename: rev
debugrevlog: changelog, manifest, dir, dump
debugrevspec: optimize, show-stage, no-optimized, verify-optimized
debugsetparents:
debugsub: rev
debugsuccessorssets:
debugtemplate: rev, define
debugupgraderepo: optimize, run
debugwalk: include, exclude
debugwireargs: three, four, five, ssh, remotecmd, insecure
files: rev, print0, include, exclude, template, subrepos
graft: rev, continue, edit, log, force, currentdate, currentuser, date, user, tool, dry-run
grep: print0, all, text, follow, ignore-case, files-with-matches, line-number, rev, user, date, template, include, exclude
heads: rev, topo, active, closed, style, template
help: extension, command, keyword, system
identify: rev, num, id, branch, tags, bookmarks, ssh, remotecmd, insecure
import: strip, base, edit, force, no-commit, bypass, partial, exact, prefix, import-branch, message, logfile, date, user, similarity
incoming: force, newest-first, bundle, rev, bookmarks, branch, patch, git, limit, no-merges, stat, graph, style, template, ssh, remotecmd, insecure, subrepos
locate: rev, print0, fullpath, include, exclude
manifest: rev, all, template
outgoing: force, rev, newest-first, bookmarks, branch, patch, git, limit, no-merges, stat, graph, style, template, ssh, remotecmd, insecure, subrepos
parents: rev, style, template
paths: template
phase: public, draft, secret, force, rev
recover:
rename: after, force, include, exclude, dry-run
resolve: all, list, mark, unmark, no-status, tool, include, exclude, template
revert: all, date, rev, no-backup, interactive, include, exclude, dry-run
rollback: dry-run, force
root:
tag: force, local, rev, remove, edit, message, date, user
tags: template
tip: patch, git, style, template
unbundle: update
verify:
version: template
$ hg init a
$ cd a
$ echo fee > fee
$ hg ci -q -Amfee
$ hg tag fee
$ mkdir fie
$ echo dead > fie/dead
$ echo live > fie/live
$ hg bookmark fo
$ hg branch -q fie
$ hg ci -q -Amfie
$ echo fo > fo
$ hg branch -qf default
$ hg ci -q -Amfo
$ echo Fum > Fum
$ hg ci -q -AmFum
$ hg bookmark Fum
Test debugpathcomplete
$ hg debugpathcomplete f
fee
fie
fo
$ hg debugpathcomplete -f f
fee
fie/dead
fie/live
fo
$ hg rm Fum
$ hg debugpathcomplete -r F
Fum
Test debugnamecomplete
$ hg debugnamecomplete
Fum
default
fee
fie
fo
tip
$ hg debugnamecomplete f
fee
fie
fo