bundle: emit full snapshot as is, without doing a redelta
With the new `forced` delta-reused policy, it become important to be able to
send full snapshot where full snapshot are needed. Otherwise, the fallback delta
will simply be used on the client side… creating monstrous delta chain, since
revision that are meant as a reset of delta-chain chain becoming too complex are
simply adding a new full delta-tree on the leaf of another one.
In the `non-forced` cases, client process full snapshot from the bundle
differently from deltas, so client will still try to convert the full snapshot
into a delta if possible. So this will no lead to pathological storage
explosion.
I have considered making this configurable, but the impact seems limited enough
that it does not seems to be worth it. Especially with the current
sparse-revlog format that use "delta-tree" with multiple level snapshots, full
snapshot are much less frequent and not that different from other intermediate
snapshot that we are already sending over the wire anyway.
CPU wise, this will help the bundling side a little as it will not need to
reconstruct revisions and compute deltas. The unbundling side might save a tiny
amount of CPU as it won't need to reconstruct the delta-base to reconstruct the
revision full text. This only slightly visible in some of the benchmarks. And
have no real impact on most of them.
### data-env-vars.name = pypy-2018-08-01-zstd-sparse-revlog
# benchmark.name = perf-bundle
# benchmark.variants.revs = last-40000
before: 11.467186 seconds
just-emit-full: 11.190576 seconds (-2.41%)
with-pull-force: 11.041091 seconds (-3.72%)
# benchmark.name = perf-unbundle
# benchmark.variants.revs = last-40000
before: 16.744862
just-emit-full:: 16.561036 seconds (-1.10%)
with-pull-force: 16.389344 seconds (-2.12%)
# benchmark.name = pull
# benchmark.variants.revs = last-40000
before: 26.870569
just-emit-full: 26.391188 seconds (-1.78%)
with-pull-force: 25.633184 seconds (-4.60%)
Space wise (so network-wise) the impact is fairly small. When taking compression into
account.
Below are tests the size of `hg bundle --all` for a handful of benchmark repositories
(with bzip, zstd compression and without it)
This show a small increase in the bundle size, but nothing really significant
except maybe for mozilla-try (+12%) that nobody really pulls large chunk of anyway.
Mozilla-try is also the repository that benefit the most for not having to
recompute deltas client size.
### mercurial:
bzip-before: 26 406 342 bytes
bzip-after: 26 691 543 bytes +1.08%
zstd-before: 27 918 645 bytes
zstd-after: 28 075 896 bytes +0.56%
none-before: 98 675 601 bytes
none-after: 100 411 237 bytes +1.76%
### pypy
bzip-before: 201 295 752 bytes
bzip-after: 209 780 282 bytes +4.21%
zstd-before: 202 974 795 bytes
zstd-after: 205 165 780 bytes +1.08%
none-before: 871 070 261 bytes
none-after: 993 595 057 bytes +14.07%
### netbeans
bzip-before: 601 314 330 bytes
bzip-after: 614 246 241 bytes +2.15%
zstd-before: 604 745 136 bytes
zstd-after: 615 497 705 bytes +1.78%
none-before: 3 338 238 571 bytes
none-after: 3 439 422 535 bytes +3.03%
### mozilla-central
bzip-before: 1 493 006 921 bytes
bzip-after: 1 549 650 570 bytes +3.79%
zstd-before: 1 481 910 102 bytes
zstd-after: 1 513 052 415 bytes +2.10%
none-before: 6 535 929 910 bytes
none-after: 7 010 191 342 bytes +7.26%
### mozilla-try
bzip-before: 6 583 425 999 bytes
bzip-after: 7 423 536 928 bytes +12.76%
zstd-before: 6 021 009 212 bytes
zstd-after: 6 674 922 420 bytes +10.86%
none-before: 22 954 739 558 bytes
none-after: 26 013 854 771 bytes +13.32%
#require baz symlink
$ baz my-id "mercurial <mercurial@mercurial-scm.org>"
$ echo "[extensions]" >> $HGRCPATH
$ echo "convert=" >> $HGRCPATH
create baz archive
$ baz make-archive baz@mercurial--convert hg-test-convert-baz
initialize baz repo
$ mkdir baz-repo
$ cd baz-repo/
$ baz init-tree baz@mercurial--convert/baz--test--0
$ baz import
* creating version baz@mercurial--convert/baz--test--0
* imported baz@mercurial--convert/baz--test--0
create initial files
$ echo 'this is a file' > a
$ baz add a
$ mkdir src
$ baz add src
$ cd src
$ dd count=1 if=/dev/zero of=b > /dev/null 2> /dev/null
$ baz add b
HACK: hide GNU tar-1.22 "tar: The --preserve option is deprecated, use --preserve-permissions --preserve-order instead"
$ baz commit -s "added a file, src and src/b (binary)" 2>&1 | grep -v '^tar'
* build pristine tree for baz@mercurial--convert/baz--test--0--base-0
* Scanning for full-tree revision: .
* from import revision: baz@mercurial--convert/baz--test--0--base-0
A/ .arch-ids
A/ src
A/ src/.arch-ids
A .arch-ids/a.id
A a
A src/.arch-ids/=id
A src/.arch-ids/b.id
A src/b
* update pristine tree (baz@mercurial--convert/baz--test--0--base-0 => baz--test--0--patch-1)
* committed baz@mercurial--convert/baz--test--0--patch-1
create link file and modify a
$ ln -s ../a a-link
$ baz add a-link
$ echo 'this a modification to a' >> ../a
$ baz commit -s "added link to a and modify a"
A src/.arch-ids/a-link.id
A src/a-link
M a
* update pristine tree (baz@mercurial--convert/baz--test--0--patch-1 => baz--test--0--patch-2)
* committed baz@mercurial--convert/baz--test--0--patch-2
create second link and modify b
$ ln -s ../a a-link-2
$ baz add a-link-2
$ dd count=1 seek=1 if=/dev/zero of=b > /dev/null 2> /dev/null
$ baz commit -s "added second link and modify b"
A src/.arch-ids/a-link-2.id
A src/a-link-2
Mb src/b
* update pristine tree (baz@mercurial--convert/baz--test--0--patch-2 => baz--test--0--patch-3)
* committed baz@mercurial--convert/baz--test--0--patch-3
b file to link and a-link-2 to regular file
$ rm -f a-link-2
$ echo 'this is now a regular file' > a-link-2
$ ln -sf ../a b
$ baz commit -s "file to link and link to file test"
fl src/b
lf src/a-link-2
* update pristine tree (baz@mercurial--convert/baz--test--0--patch-3 => baz--test--0--patch-4)
* committed baz@mercurial--convert/baz--test--0--patch-4
move a-link-2 file and src directory
$ cd ..
$ baz mv src/a-link-2 c
$ baz mv src test
$ baz commit -s "move and rename a-link-2 file and src directory"
D/ src/.arch-ids
A/ test/.arch-ids
/> src test
=> src/.arch-ids/a-link-2.id .arch-ids/c.id
=> src/a-link-2 c
=> src/.arch-ids/=id test/.arch-ids/=id
=> src/.arch-ids/a-link.id test/.arch-ids/a-link.id
=> src/.arch-ids/b.id test/.arch-ids/b.id
* update pristine tree (baz@mercurial--convert/baz--test--0--patch-4 => baz--test--0--patch-5)
* committed baz@mercurial--convert/baz--test--0--patch-5
move and add the moved file again
$ echo e > e
$ baz add e
$ baz commit -s "add e"
A .arch-ids/e.id
A e
* update pristine tree (baz@mercurial--convert/baz--test--0--patch-5 => baz--test--0--patch-6)
* committed baz@mercurial--convert/baz--test--0--patch-6
$ baz mv e f
$ echo ee > e
$ baz add e
$ baz commit -s "move e and recreate it again"
A .arch-ids/e.id
A e
=> .arch-ids/e.id .arch-ids/f.id
=> e f
* update pristine tree (baz@mercurial--convert/baz--test--0--patch-6 => baz--test--0--patch-7)
* committed baz@mercurial--convert/baz--test--0--patch-7
$ cd ..
converting baz repo to Mercurial
$ hg convert baz-repo baz-repo-hg
initializing destination baz-repo-hg repository
analyzing tree version baz@mercurial--convert/baz--test--0...
scanning source...
sorting...
converting...
7 initial import
6 added a file, src and src/b (binary)
5 added link to a and modify a
4 added second link and modify b
3 file to link and link to file test
2 move and rename a-link-2 file and src directory
1 add e
0 move e and recreate it again
$ baz register-archive -d baz@mercurial--convert
$ glog()
> {
> hg log -G --template '{rev} "{desc|firstline}" files: {files}\n' "$@"
> }
show graph log
$ glog -R baz-repo-hg
o 7 "move e and recreate it again" files: e f
|
o 6 "add e" files: e
|
o 5 "move and rename a-link-2 file and src directory" files: c src/a-link src/a-link-2 src/b test/a-link test/b
|
o 4 "file to link and link to file test" files: src/a-link-2 src/b
|
o 3 "added second link and modify b" files: src/a-link-2 src/b
|
o 2 "added link to a and modify a" files: a src/a-link
|
o 1 "added a file, src and src/b (binary)" files: a src/b
|
o 0 "initial import" files:
$ hg up -q -R baz-repo-hg
$ hg -R baz-repo-hg manifest --debug
c4072c4b72e1cabace081888efa148ee80ca3cbb 644 a
0201ac32a3a8e86e303dff60366382a54b48a72e 644 c
1a4a864db0073705a11b1439f563bfa4b46d9246 644 e
09e0222742fc3f75777fa9d68a5d8af7294cb5e7 644 f
c0067ba5ff0b7c9a3eb17270839d04614c435623 644 @ test/a-link
375f4263d86feacdea7e3c27100abd1560f2a973 644 @ test/b
$ hg -R baz-repo-hg log -r 5 -r 7 -C --debug | grep copies
copies: c (src/a-link-2) test/a-link (src/a-link) test/b (src/b)
copies: f (e)