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
stages:
- tests
image: registry.heptapod.net/mercurial/ci-images/mercurial-core:$HG_CI_IMAGE_TAG
variables:
PYTHON: python
TEST_HGMODULEPOLICY: "allow"
HG_CI_IMAGE_TAG: "v1.0"
TEST_HGTESTS_ALLOW_NETIO: "0"
.all_template: &all
when: on_success
.runtests_template: &runtests
<<: *all
stage: tests
# The runner made a clone as root.
# We make a new clone owned by user used to run the step.
before_script:
- hg clone . /tmp/mercurial-ci/ --noupdate --config phases.publish=no
- hg -R /tmp/mercurial-ci/ update `hg log --rev '.' --template '{node}'`
- cd /tmp/mercurial-ci/
- ls -1 tests/test-check-*.* > /tmp/check-tests.txt
- black --version
- clang-format --version
script:
- echo "python used, $PYTHON"
- echo "$RUNTEST_ARGS"
- HGTESTS_ALLOW_NETIO="$TEST_HGTESTS_ALLOW_NETIO" HGMODULEPOLICY="$TEST_HGMODULEPOLICY" "$PYTHON" tests/run-tests.py --color=always $RUNTEST_ARGS
checks:
<<: *runtests
variables:
RUNTEST_ARGS: "--time --test-list /tmp/check-tests.txt"
PYTHON: python3
rust-cargo-test:
<<: *all
stage: tests
script:
- echo "python used, $PYTHON"
- make rust-tests
variables:
PYTHON: python3
test-c:
<<: *runtests
variables:
RUNTEST_ARGS: " --no-rust --blacklist /tmp/check-tests.txt"
PYTHON: python3
TEST_HGMODULEPOLICY: "c"
TEST_HGTESTS_ALLOW_NETIO: "1"
test-pure:
<<: *runtests
variables:
RUNTEST_ARGS: "--pure --blacklist /tmp/check-tests.txt"
PYTHON: python3
TEST_HGMODULEPOLICY: "py"
test-rust:
<<: *runtests
variables:
HGWITHRUSTEXT: cpython
RUNTEST_ARGS: "--rust --blacklist /tmp/check-tests.txt"
PYTHON: python3
TEST_HGMODULEPOLICY: "rust+c"
test-rhg:
<<: *runtests
variables:
HGWITHRUSTEXT: cpython
RUNTEST_ARGS: "--rust --rhg --blacklist /tmp/check-tests.txt"
PYTHON: python3
TEST_HGMODULEPOLICY: "rust+c"
test-chg:
<<: *runtests
variables:
PYTHON: python3
RUNTEST_ARGS: "--blacklist /tmp/check-tests.txt --chg"
TEST_HGMODULEPOLICY: "c"
check-pytype:
extends: .runtests_template
before_script:
- hg clone . /tmp/mercurial-ci/ --noupdate --config phases.publish=no
- hg -R /tmp/mercurial-ci/ update `hg log --rev '.' --template '{node}'`
- cd /tmp/mercurial-ci/
- make local PYTHON=$PYTHON
- $PYTHON -m pip install --user -U libcst==0.3.20 pytype==2022.03.29
variables:
RUNTEST_ARGS: " --allow-slow-tests tests/test-check-pytype.t"
HGTEST_SLOWTIMEOUT: "3600"
PYTHON: python3
TEST_HGMODULEPOLICY: "c"
# `sh.exe --login` sets a couple of extra environment variables that are defined
# in the MinGW shell, but switches CWD to /home/$username. The previous value
# is stored in OLDPWD. Of the added variables, MSYSTEM is crucial to running
# run-tests.py- it is needed to make run-tests.py generate a `python3` script
# that satisfies the various shebang lines and delegates to `py -3`.
.window_runtests_template: &windows_runtests
<<: *all
when: manual # we don't have any Windows runners anymore at the moment
stage: tests
before_script:
- C:/MinGW/msys/1.0/bin/sh.exe --login -c 'cd "$OLDPWD" && ls -1 tests/test-check-*.* > C:/Temp/check-tests.txt'
# TODO: find/install cvs, bzr, perforce, gpg, sqlite3
script:
- echo "Entering script section"
- echo "python used, $Env:PYTHON"
- Invoke-Expression "$Env:PYTHON -V"
- Invoke-Expression "$Env:PYTHON -m black --version"
- echo "$Env:RUNTEST_ARGS"
- echo "$Env:TMP"
- echo "$Env:TEMP"
- C:/MinGW/msys/1.0/bin/sh.exe --login -c 'cd "$OLDPWD" && HGTESTS_ALLOW_NETIO="$TEST_HGTESTS_ALLOW_NETIO" HGMODULEPOLICY="$TEST_HGMODULEPOLICY" $PYTHON tests/run-tests.py --color=always $RUNTEST_ARGS'
windows:
<<: *windows_runtests
tags:
- windows
variables:
TEST_HGMODULEPOLICY: "c"
RUNTEST_ARGS: "--blacklist C:/Temp/check-tests.txt"
PYTHON: py -3
windows-pyox:
<<: *windows_runtests
tags:
- windows
variables:
TEST_HGMODULEPOLICY: "c"
RUNTEST_ARGS: "--blacklist C:/Temp/check-tests.txt --pyoxidized"
PYTHON: py -3