sparse-revlog: implement algorithm to write sparse delta chains (
issue5480)
The classic behavior of revlog._isgooddeltainfo is to consider the span size
of the whole delta chain, and limit it to 4 * textlen.
Once sparse-revlog writing is allowed (and enforced with a requirement),
revlog._isgooddeltainfo considers the span of the largest chunk as the
distance used in the verification, instead of using the span of the whole
delta chain.
In order to compute the span of the largest chunk, we need to slice into
chunks a chain with the new revision at the top of the revlog, and take the
maximal span of these chunks. The sparse read density is a parameter to the
slicing, as it will stop when the global read density reaches this threshold.
For instance, a density of 50% means that 2 of 4 read bytes are actually used
for the reconstruction of the revision (the others are part of other chains).
This allows a new revision to be potentially stored with a diff against
another revision anywhere in the history, instead of forcing it in the last 4
* textlen. The result is a much better compression on repositories that have
many concurrent branches. Here are a comparison between using deltas from
current upstream (aggressive-merge-deltas on by default) and deltas from a
sparse-revlog
Comparison of `.hg/store/` size:
mercurial (6.74% merges):
before: 46,831,873 bytes
after: 46,795,992 bytes (no relevant change)
pypy (8.30% merges):
before: 333,524,651 bytes
after: 308,417,511 bytes -8%
netbeans (34.21% merges):
before: 1,141,847,554 bytes
after: 1,131,093,161 bytes -1%
mozilla-central (4.84% merges):
before: 2,344,248,850 bytes
after: 2,328,459,258 bytes -1%
large-private-repo-A (merge 19.73%)
before: 41,510,550,163 bytes
after: 8,121,763,428 bytes -80%
large-private-repo-B (23.77%)
before: 58,702,221,709 bytes
after: 8,351,588,828 bytes -76%
Comparison of `00manifest.d` size:
mercurial (6.74% merges):
before: 6,143,044 bytes
after: 6,107,163 bytes
pypy (8.30% merges):
before: 52,941,780 bytes
after: 27,834,082 bytes -48%
netbeans (34.21% merges):
before: 130,088,982 bytes
after: 119,337,636 bytes -10%
mozilla-central (4.84% merges):
before: 215,096,339 bytes
after: 199,496,863 bytes -8%
large-private-repo-A (merge 19.73%)
before: 33,725,285,081 bytes
after: 390,302,545 bytes -99%
large-private-repo-B (23.77%)
before: 49,457,701,645 bytes
after: 1,366,752,187 bytes -97%
The better delta chains provide a performance boost in relevant repositories:
pypy, bundling 1000 revisions:
before: 1.670s
after: 1.149s -31%
Unbundling got a bit slower. probably because the sparse algorithm is still
pure
python.
pypy, unbundling 1000 revisions:
before: 4.062s
after: 4.507s +10%
Performance of bundle/unbundle in repository with few concurrent branches (eg:
mercurial) are unaffected.
No significant differences have been noticed then timing `hg push` and `hg
pull` locally. More state timings are being gathered.
Same as for aggressive-merge-delta, better delta comes with longer delta
chains. Longer chains have a performance impact. For example. The length of
the chain needed to get the manifest of pypy's tip moves from 82 item to 1929
items. This moves the restore time from 3.88ms to 11.3ms.
Delta chain length is an independent issue that affects repository without
this changes. It will be dealt with independently.
No significant differences have been observed on repositories where
`sparse-revlog` have not much effect (mercurial, unity, netbeans). On pypy,
small differences have been observed on some operation affected by delta chain
building and retrieval.
pypy, perfmanifest
before: 0.006162s
after: 0.017899s +190%
pypy, commit:
before: 0.382
after: 0.376 -1%
pypy, status:
before: 0.157
after: 0.168 +7%
More comprehensive and stable timing comparisons are in progress.
$ cat >> $HGRCPATH <<EOF
> [extensions]
> rebase=
> histedit=
>
> [alias]
> tglog = log -G --template "{rev}: {node|short} '{desc}' {branches}\n"
> EOF
$ hg init a
$ cd a
$ echo C1 > C1
$ hg ci -Am C1
adding C1
$ echo C2 > C2
$ hg ci -Am C2
adding C2
$ cd ..
$ hg clone a b
updating to branch default
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg clone a c
updating to branch default
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cd b
$ echo L1 > L1
$ hg ci -Am L1
adding L1
$ cd ../a
$ echo R1 > R1
$ hg ci -Am R1
adding R1
$ cd ../b
Now b has one revision to be pulled from a:
$ hg pull --rebase
pulling from $TESTTMP/a
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files (+1 heads)
new changesets 77ae9631bcca
rebasing 2:ff8d69a621f9 "L1"
saved backup bundle to $TESTTMP/b/.hg/strip-backup/ff8d69a621f9-160fa373-rebase.hg
$ hg tglog
@ 3: d80cc2da061e 'L1'
|
o 2: 77ae9631bcca 'R1'
|
o 1: 783333faa078 'C2'
|
o 0: 05d58a0c15dd 'C1'
Re-run:
$ hg pull --rebase
pulling from $TESTTMP/a
searching for changes
no changes found
Abort pull early if working dir is not clean:
$ echo L1-mod > L1
$ hg pull --rebase
abort: uncommitted changes
(cannot pull with rebase: please commit or shelve your changes first)
[255]
$ hg update --clean --quiet
Abort pull early if another operation (histedit) is in progress:
$ hg histedit . -q --commands - << EOF
> edit d80cc2da061e histedit: generate unfinished state
> EOF
Editing (d80cc2da061e), you may commit or record as needed now.
(hg histedit --continue to resume)
[1]
$ hg pull --rebase
abort: histedit in progress
(use 'hg histedit --continue' or 'hg histedit --abort')
[255]
$ hg histedit --abort --quiet
Abort pull early with pending uncommitted merge:
$ cd ..
$ hg clone --noupdate c d
$ cd d
$ hg tglog
o 1: 783333faa078 'C2'
|
o 0: 05d58a0c15dd 'C1'
$ hg update --quiet 0
$ echo M1 > M1
$ hg commit --quiet -Am M1
$ hg update --quiet 1
$ hg merge 2
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg pull --rebase
abort: outstanding uncommitted merge
(cannot pull with rebase: please commit or shelve your changes first)
[255]
$ hg update --clean --quiet
Abort pull early with unclean subrepo:
$ echo s = s > .hgsub
$ hg add .hgsub
$ hg init s
$ hg commit -m "generated a subrepo"
$ echo a > s/a
$ hg -R s add s/a
$ hg pull --rebase
abort: uncommitted changes in subrepository "s"
(cannot pull with rebase: please commit or shelve your changes first)
[255]
Invoke pull --rebase and nothing to rebase:
$ cd ../c
$ hg book norebase
$ hg pull --rebase
pulling from $TESTTMP/a
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files
new changesets 77ae9631bcca
nothing to rebase - updating instead
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
updating bookmark norebase
$ hg tglog -l 1
@ 2: 77ae9631bcca 'R1'
|
~
pull --rebase --update should ignore --update:
$ hg pull --rebase --update
pulling from $TESTTMP/a
searching for changes
no changes found
pull --rebase doesn't update if nothing has been pulled:
$ hg up -q 1
$ hg pull --rebase
pulling from $TESTTMP/a
searching for changes
no changes found
$ hg tglog -l 1
o 2: 77ae9631bcca 'R1'
|
~
$ cd ..
pull --rebase works when a specific revision is pulled (issue3619)
$ cd a
$ hg tglog
@ 2: 77ae9631bcca 'R1'
|
o 1: 783333faa078 'C2'
|
o 0: 05d58a0c15dd 'C1'
$ echo R2 > R2
$ hg ci -Am R2
adding R2
$ echo R3 > R3
$ hg ci -Am R3
adding R3
$ cd ../c
$ hg tglog
o 2: 77ae9631bcca 'R1'
|
@ 1: 783333faa078 'C2'
|
o 0: 05d58a0c15dd 'C1'
$ echo L1 > L1
$ hg ci -Am L1
adding L1
created new head
$ hg pull --rev tip --rebase
pulling from $TESTTMP/a
searching for changes
adding changesets
adding manifests
adding file changes
added 2 changesets with 2 changes to 2 files
new changesets 31cd3a05214e:770a61882ace
rebasing 3:ff8d69a621f9 "L1"
saved backup bundle to $TESTTMP/c/.hg/strip-backup/ff8d69a621f9-160fa373-rebase.hg
$ hg tglog
@ 5: 518d153c0ba3 'L1'
|
o 4: 770a61882ace 'R3'
|
o 3: 31cd3a05214e 'R2'
|
o 2: 77ae9631bcca 'R1'
|
o 1: 783333faa078 'C2'
|
o 0: 05d58a0c15dd 'C1'
pull --rebase works with bundle2 turned on
$ cd ../a
$ echo R4 > R4
$ hg ci -Am R4
adding R4
$ hg tglog
@ 5: 00e3b7781125 'R4'
|
o 4: 770a61882ace 'R3'
|
o 3: 31cd3a05214e 'R2'
|
o 2: 77ae9631bcca 'R1'
|
o 1: 783333faa078 'C2'
|
o 0: 05d58a0c15dd 'C1'
$ cd ../c
$ hg pull --rebase
pulling from $TESTTMP/a
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files (+1 heads)
new changesets 00e3b7781125
rebasing 5:518d153c0ba3 "L1"
saved backup bundle to $TESTTMP/c/.hg/strip-backup/518d153c0ba3-73407f14-rebase.hg
$ hg tglog
@ 6: 0d0727eb7ce0 'L1'
|
o 5: 00e3b7781125 'R4'
|
o 4: 770a61882ace 'R3'
|
o 3: 31cd3a05214e 'R2'
|
o 2: 77ae9631bcca 'R1'
|
o 1: 783333faa078 'C2'
|
o 0: 05d58a0c15dd 'C1'
pull --rebase only update if there is nothing to rebase
$ cd ../a
$ echo R5 > R5
$ hg ci -Am R5
adding R5
$ hg tglog
@ 6: 88dd24261747 'R5'
|
o 5: 00e3b7781125 'R4'
|
o 4: 770a61882ace 'R3'
|
o 3: 31cd3a05214e 'R2'
|
o 2: 77ae9631bcca 'R1'
|
o 1: 783333faa078 'C2'
|
o 0: 05d58a0c15dd 'C1'
$ cd ../c
$ echo L2 > L2
$ hg ci -Am L2
adding L2
$ hg up 'desc(L1)'
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ hg pull --rebase
pulling from $TESTTMP/a
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files (+1 heads)
new changesets 88dd24261747
rebasing 6:0d0727eb7ce0 "L1"
rebasing 7:c1f58876e3bf "L2"
saved backup bundle to $TESTTMP/c/.hg/strip-backup/0d0727eb7ce0-ef61ccb2-rebase.hg
$ hg tglog
o 8: 6dc0ea5dcf55 'L2'
|
@ 7: 864e0a2d2614 'L1'
|
o 6: 88dd24261747 'R5'
|
o 5: 00e3b7781125 'R4'
|
o 4: 770a61882ace 'R3'
|
o 3: 31cd3a05214e 'R2'
|
o 2: 77ae9631bcca 'R1'
|
o 1: 783333faa078 'C2'
|
o 0: 05d58a0c15dd 'C1'
pull --rebase update (no rebase) use proper update:
- warn about other head.
$ cd ../a
$ echo R6 > R6
$ hg ci -Am R6
adding R6
$ cd ../c
$ hg up 'desc(R5)'
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ hg pull --rebase
pulling from $TESTTMP/a
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files (+1 heads)
new changesets 65bc164c1d9b
nothing to rebase - updating instead
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
updated to "65bc164c1d9b: R6"
1 other heads for branch "default"
$ hg tglog
@ 9: 65bc164c1d9b 'R6'
|
| o 8: 6dc0ea5dcf55 'L2'
| |
| o 7: 864e0a2d2614 'L1'
|/
o 6: 88dd24261747 'R5'
|
o 5: 00e3b7781125 'R4'
|
o 4: 770a61882ace 'R3'
|
o 3: 31cd3a05214e 'R2'
|
o 2: 77ae9631bcca 'R1'
|
o 1: 783333faa078 'C2'
|
o 0: 05d58a0c15dd 'C1'
Multiple pre-existing heads on the branch
-----------------------------------------
Pull bring content, but nothing on the current branch, we should not consider
pre-existing heads.
$ cd ../a
$ hg branch unrelatedbranch
marked working directory as branch unrelatedbranch
(branches are permanent and global, did you want a bookmark?)
$ echo B1 > B1
$ hg commit -Am B1
adding B1
$ cd ../c
$ hg up 'desc(L2)'
2 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ hg pull --rebase
pulling from $TESTTMP/a
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files
new changesets 39c381359968
nothing to rebase
There is two local heads and we pull a third one.
The second local head should not confuse the `hg pull rebase`.
$ hg up 'desc(R6)'
1 files updated, 0 files merged, 2 files removed, 0 files unresolved
$ echo M1 > M1
$ hg commit -Am M1
adding M1
$ cd ../a
$ hg up 'desc(R6)'
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ echo R7 > R7
$ hg commit -Am R7
adding R7
$ cd ../c
$ hg up 'desc(L2)'
2 files updated, 0 files merged, 2 files removed, 0 files unresolved
$ hg pull --rebase
pulling from $TESTTMP/a
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files (+1 heads)
new changesets f7d3e42052f9
rebasing 7:864e0a2d2614 "L1"
rebasing 8:6dc0ea5dcf55 "L2"
saved backup bundle to $TESTTMP/c/.hg/strip-backup/864e0a2d2614-2f72c89c-rebase.hg
$ hg tglog
@ 12: 3603a865eea0 'L2'
|
o 11: bcc8a9cd04bf 'L1'
|
o 10: f7d3e42052f9 'R7'
|
| o 9: 41fab4eef82f 'M1'
|/
| o 8: 39c381359968 'B1' unrelatedbranch
|/
o 7: 65bc164c1d9b 'R6'
|
o 6: 88dd24261747 'R5'
|
o 5: 00e3b7781125 'R4'
|
o 4: 770a61882ace 'R3'
|
o 3: 31cd3a05214e 'R2'
|
o 2: 77ae9631bcca 'R1'
|
o 1: 783333faa078 'C2'
|
o 0: 05d58a0c15dd 'C1'