bisect: avoid copying ancestor list for non-merge commits
During a bisection, hg needs to compute a list of all ancestors for every
candidate commit. This is accomplished via a bottom-up traversal of the set of
candidates, during which each revision's ancestor list is populated using the
ancestor list of its parent(s). Previously, this involved copying the entire
list, which could be very long in if the bisection range was large.
To help improve this, we can observe that each candidate commit is visited
exactly once, at which point its ancestor list is copied into its children's
lists and then dropped. In the case of non-merge commits, a commit's ancestor
list consists exactly of its parent's list plus itself. This means that we can
trivially reuse the parent's existing list for one of its non-merge children,
which avoids copying entirely if that commit is the parent's only child. This
makes bisections over linear ranges of commits much faster.
During some informal testing in the large publicly-available `mozilla-central`
repository, this noticeably sped up bisections over large ranges of history:
Setup:
$ cd mozilla-central
$ hg bisect --reset
$ hg bisect --good 0
$ hg log -r tip -T '{rev}\n'
628417
Test:
$ time hg bisect --bad tip --noupdate
Before:
real 3m35.927s
user 3m35.553s
sys 0m0.319s
After:
real 1m41.142s
user 1m40.810s
sys 0m0.285s
#require no-reposimplestore
Test creating a consuming stream bundle v2
$ getmainid() {
> hg -R main log --template '{node}\n' --rev "$1"
> }
$ cp $HGRCPATH $TESTTMP/hgrc.orig
$ cat >> $HGRCPATH << EOF
> [experimental]
> evolution.createmarkers=True
> evolution.exchange=True
> bundle2-output-capture=True
> [ui]
> logtemplate={rev}:{node|short} {phase} {author} {bookmarks} {desc|firstline}
> [web]
> push_ssl = false
> allow_push = *
> [phases]
> publish=False
> [extensions]
> drawdag=$TESTDIR/drawdag.py
> clonebundles=
> EOF
The extension requires a repo (currently unused)
$ hg init main
$ cd main
$ hg debugdrawdag <<'EOF'
> E
> |
> D
> |
> C
> |
> B
> |
> A
> EOF
$ hg bundle -a --type="none-v2;stream=v2" bundle.hg
$ hg debugbundle bundle.hg
Stream params: {}
stream2 -- {bytecount: 1693, filecount: 11, requirements: generaldelta%2Crevlogv1%2Csparserevlog} (mandatory: True) (no-zstd !)
stream2 -- {bytecount: 1693, filecount: 11, requirements: generaldelta%2Crevlog-compression-zstd%2Crevlogv1%2Csparserevlog} (mandatory: True) (zstd no-rust !)
stream2 -- {bytecount: 1693, filecount: 11, requirements: generaldelta%2Crevlog-compression-zstd%2Crevlogv1%2Csparserevlog} (mandatory: True) (rust !)
$ hg debugbundle --spec bundle.hg
none-v2;stream=v2;requirements%3Dgeneraldelta%2Crevlogv1%2Csparserevlog (no-zstd !)
none-v2;stream=v2;requirements%3Dgeneraldelta%2Crevlog-compression-zstd%2Crevlogv1%2Csparserevlog (zstd no-rust !)
none-v2;stream=v2;requirements%3Dgeneraldelta%2Crevlog-compression-zstd%2Crevlogv1%2Csparserevlog (rust !)
Test that we can apply the bundle as a stream clone bundle
$ cat > .hg/clonebundles.manifest << EOF
> http://localhost:$HGPORT1/bundle.hg BUNDLESPEC=`hg debugbundle --spec bundle.hg`
> EOF
$ hg serve -d -p $HGPORT --pid-file hg.pid --accesslog access.log
$ cat hg.pid >> $DAEMON_PIDS
$ "$PYTHON" $TESTDIR/dumbhttp.py -p $HGPORT1 --pid http.pid
$ cat http.pid >> $DAEMON_PIDS
$ cd ..
$ hg clone http://localhost:$HGPORT streamv2-clone-implicit --debug
using http://localhost:$HGPORT/
sending capabilities command
sending clonebundles command
applying clone bundle from http://localhost:$HGPORT1/bundle.hg
bundle2-input-bundle: with-transaction
bundle2-input-part: "stream2" (params: 3 mandatory) supported
applying stream bundle
11 files to transfer, 1.65 KB of data
starting 4 threads for background file closing (?)
starting 4 threads for background file closing (?)
adding [s] data/A.i (66 bytes)
adding [s] data/B.i (66 bytes)
adding [s] data/C.i (66 bytes)
adding [s] data/D.i (66 bytes)
adding [s] data/E.i (66 bytes)
adding [s] 00manifest.i (584 bytes)
adding [s] 00changelog.i (595 bytes)
adding [s] phaseroots (43 bytes)
adding [c] branch2-served (94 bytes)
adding [c] rbc-names-v1 (7 bytes)
adding [c] rbc-revs-v1 (40 bytes)
transferred 1.65 KB in * seconds (* */sec) (glob)
bundle2-input-part: total payload size 1840
bundle2-input-bundle: 1 parts total
updating the branch cache
finished applying clone bundle
query 1; heads
sending batch command
searching for changes
all remote heads known locally
no changes found
sending getbundle command
bundle2-input-bundle: with-transaction
bundle2-input-part: "listkeys" (params: 1 mandatory) supported
bundle2-input-part: "phase-heads" supported
bundle2-input-part: total payload size 24
bundle2-input-bundle: 2 parts total
checking for updated bookmarks
updating to branch default
resolving manifests
branchmerge: False, force: False, partial: False
ancestor: 000000000000, local: 000000000000+, remote: 9bc730a19041
A: remote created -> g
getting A
B: remote created -> g
getting B
C: remote created -> g
getting C
D: remote created -> g
getting D
E: remote created -> g
getting E
5 files updated, 0 files merged, 0 files removed, 0 files unresolved
updating the branch cache
(sent 4 HTTP requests and * bytes; received * bytes in responses) (glob)
$ hg clone --stream http://localhost:$HGPORT streamv2-clone-explicit --debug
using http://localhost:$HGPORT/
sending capabilities command
sending clonebundles command
applying clone bundle from http://localhost:$HGPORT1/bundle.hg
bundle2-input-bundle: with-transaction
bundle2-input-part: "stream2" (params: 3 mandatory) supported
applying stream bundle
11 files to transfer, 1.65 KB of data
starting 4 threads for background file closing (?)
starting 4 threads for background file closing (?)
adding [s] data/A.i (66 bytes)
adding [s] data/B.i (66 bytes)
adding [s] data/C.i (66 bytes)
adding [s] data/D.i (66 bytes)
adding [s] data/E.i (66 bytes)
adding [s] 00manifest.i (584 bytes)
adding [s] 00changelog.i (595 bytes)
adding [s] phaseroots (43 bytes)
adding [c] branch2-served (94 bytes)
adding [c] rbc-names-v1 (7 bytes)
adding [c] rbc-revs-v1 (40 bytes)
transferred 1.65 KB in * seconds (* */sec) (glob)
bundle2-input-part: total payload size 1840
bundle2-input-bundle: 1 parts total
updating the branch cache
finished applying clone bundle
query 1; heads
sending batch command
searching for changes
all remote heads known locally
no changes found
sending getbundle command
bundle2-input-bundle: with-transaction
bundle2-input-part: "listkeys" (params: 1 mandatory) supported
bundle2-input-part: "phase-heads" supported
bundle2-input-part: total payload size 24
bundle2-input-bundle: 2 parts total
checking for updated bookmarks
updating to branch default
resolving manifests
branchmerge: False, force: False, partial: False
ancestor: 000000000000, local: 000000000000+, remote: 9bc730a19041
A: remote created -> g
getting A
B: remote created -> g
getting B
C: remote created -> g
getting C
D: remote created -> g
getting D
E: remote created -> g
getting E
5 files updated, 0 files merged, 0 files removed, 0 files unresolved
updating the branch cache
(sent 4 HTTP requests and * bytes; received * bytes in responses) (glob)