cborutil: change buffering strategy
Profiling revealed that we were spending a lot of time on the
line that was concatenating the old buffer with the incoming data
when attempting to decode long byte strings, such as manifest
revisions.
Essentially, we were feeding N chunks of size len(X) << len(Y) into
decode() and continuously allocating a new, larger buffer to hold
the undecoded input. This created substantial memory churn and
slowed down execution.
Changing the code to aggregate pending chunks in a list until we
have enough data to fully decode the next atom makes things much
more efficient.
I don't have exact data, but I recall the old code spending >1s
on manifest fulltexts from the mozilla-unified repo. The new code
doesn't significantly appear in profile output.
Differential Revision: https://phab.mercurial-scm.org/D4854
Rebasing using a single transaction
$ cat >> $HGRCPATH <<EOF
> [extensions]
> rebase=
> drawdag=$TESTDIR/drawdag.py
>
> [rebase]
> singletransaction=True
>
> [phases]
> publish=False
>
> [alias]
> tglog = log -G --template "{rev}: {desc}"
> EOF
Check that a simple rebase works
$ hg init simple && cd simple
$ hg debugdrawdag <<'EOF'
> Z
> |
> | D
> | |
> | C
> | |
> Y B
> |/
> A
> EOF
- We should only see one status stored message. It comes from the start.
$ hg rebase --debug -b D -d Z | grep 'status stored'
rebase status stored
$ hg tglog
o 5: D
|
o 4: C
|
o 3: B
|
o 2: Z
|
o 1: Y
|
o 0: A
$ cd ..
Check that --collapse works
$ hg init collapse && cd collapse
$ hg debugdrawdag <<'EOF'
> Z
> |
> | D
> | |
> | C
> | |
> Y B
> |/
> A
> EOF
- We should only see two status stored messages. One from the start, one from
- cmdutil.commitforceeditor() which forces tr.writepending()
$ hg rebase --collapse --debug -b D -d Z | grep 'status stored'
rebase status stored
rebase status stored
$ hg tglog
o 3: Collapsed revision
| * B
| * C
| * D
o 2: Z
|
o 1: Y
|
o 0: A
$ cd ..
With --collapse, check that conflicts can be resolved and rebase can then be
continued
$ hg init collapse-conflict && cd collapse-conflict
$ hg debugdrawdag <<'EOF'
> Z # Z/conflict=Z
> |
> | D
> | |
> | C # C/conflict=C
> | |
> Y B
> |/
> A
> EOF
$ hg rebase --collapse -b D -d Z
rebasing 1:112478962961 "B" (B)
rebasing 3:c26739dbe603 "C" (C)
merging conflict
warning: conflicts while merging conflict! (edit, then use 'hg resolve --mark')
unresolved conflicts (see hg resolve, then hg rebase --continue)
[1]
$ hg tglog
o 5: D
|
| @ 4: Z
| |
@ | 3: C
| |
| o 2: Y
| |
o | 1: B
|/
o 0: A
$ hg st
M C
M conflict
A B
? conflict.orig
$ echo resolved > conflict
$ hg resolve -m
(no more unresolved files)
continue: hg rebase --continue
$ hg rebase --continue
already rebased 1:112478962961 "B" (B) as 79bc8f4973ce
rebasing 3:c26739dbe603 "C" (C)
rebasing 5:d24bb333861c "D" (D tip)
saved backup bundle to $TESTTMP/collapse-conflict/.hg/strip-backup/112478962961-b5b34645-rebase.hg
$ hg tglog
o 3: Collapsed revision
| * B
| * C
| * D
o 2: Z
|
o 1: Y
|
o 0: A
$ cd ..
With --collapse, check that the commit message editing can be canceled and
rebase can then be continued
$ hg init collapse-cancel-editor && cd collapse-cancel-editor
$ hg debugdrawdag <<'EOF'
> Z
> |
> | D
> | |
> | C
> | |
> Y B
> |/
> A
> EOF
$ HGEDITOR=false hg --config ui.interactive=1 rebase --collapse -b D -d Z
rebasing 1:112478962961 "B" (B)
rebasing 3:26805aba1e60 "C" (C)
rebasing 5:f585351a92f8 "D" (D tip)
transaction abort!
rollback completed
abort: edit failed: false exited with status 1
[255]
$ hg tglog
o 5: D
|
| o 4: Z
| |
o | 3: C
| |
| o 2: Y
| |
o | 1: B
|/
o 0: A
$ hg rebase --continue
rebasing 1:112478962961 "B" (B)
rebasing 3:26805aba1e60 "C" (C)
rebasing 5:f585351a92f8 "D" (D tip)
saved backup bundle to $TESTTMP/collapse-cancel-editor/.hg/strip-backup/112478962961-cb2a9b47-rebase.hg
$ hg tglog
o 3: Collapsed revision
| * B
| * C
| * D
o 2: Z
|
o 1: Y
|
o 0: A
$ cd ..