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-chg
$ filterlog () {
> sed -e 's!^[0-9/]* [0-9:]* ([0-9]*)>!YYYY/MM/DD HH:MM:SS (PID)>!'
> }
ensure that failing ui.atexit handlers report sensibly
$ cat > $TESTTMP/bailatexit.py <<EOF
> from mercurial import util
> def bail():
> raise RuntimeError('ui.atexit handler exception')
>
> def extsetup(ui):
> ui.atexit(bail)
> EOF
$ hg -q --config extensions.bailatexit=$TESTTMP/bailatexit.py \
> help help
hg help [-eck] [-s PLATFORM] [TOPIC]
show help for a given topic or a help overview
error in exit handlers:
Traceback (most recent call last):
File "*/mercurial/dispatch.py", line *, in _runexithandlers (glob) (no-pyoxidizer !)
File "mercurial.dispatch", line *, in _runexithandlers (glob) (pyoxidizer !)
func(*args, **kwargs)
File "$TESTTMP/bailatexit.py", line *, in bail (glob)
raise RuntimeError('ui.atexit handler exception')
RuntimeError: ui.atexit handler exception
[255]
$ rm $TESTTMP/bailatexit.py
another bad extension
$ echo 'raise Exception("bit bucket overflow")' > badext.py
$ abspathexc=`pwd`/badext.py
$ cat >baddocext.py <<EOF
> """
> baddocext is bad
> """
> EOF
$ abspathdoc=`pwd`/baddocext.py
$ cat <<EOF >> $HGRCPATH
> [extensions]
> gpg =
> hgext.gpg =
> badext = $abspathexc
> baddocext = $abspathdoc
> badext2 =
> EOF
$ hg -q help help 2>&1 |grep extension
*** failed to import extension "badext" from $TESTTMP/badext.py: bit bucket overflow
*** failed to import extension "badext2": No module named 'badext2' (py3 !)
show traceback
$ hg -q help help --traceback 2>&1 | egrep ' extension|^Exception|Traceback|ImportError|ModuleNotFound'
*** failed to import extension "badext" from $TESTTMP/badext.py: bit bucket overflow
Traceback (most recent call last):
Exception: bit bucket overflow
*** failed to import extension "badext2": No module named 'badext2' (py3 !)
Traceback (most recent call last):
ImportError: No module named 'hgext.badext2' (py3 no-py36 !)
ModuleNotFoundError: No module named 'hgext.badext2' (py36 !)
Traceback (most recent call last): (py3 !)
ImportError: No module named 'hgext3rd.badext2' (py3 no-py36 !)
ModuleNotFoundError: No module named 'hgext3rd.badext2' (py36 !)
Traceback (most recent call last): (py3 !)
ImportError: No module named 'badext2' (py3 no-py36 !)
ModuleNotFoundError: No module named 'badext2' (py36 !)
names of extensions failed to load can be accessed via extensions.notloaded()
$ cat <<EOF > showbadexts.py
> from mercurial import commands, extensions, registrar
> cmdtable = {}
> command = registrar.command(cmdtable)
> @command(b'showbadexts', norepo=True)
> def showbadexts(ui, *pats, **opts):
> ui.write(b'BADEXTS: %s\n' % b' '.join(sorted(extensions.notloaded())))
> EOF
$ hg --config extensions.badexts=showbadexts.py showbadexts 2>&1 | grep '^BADEXTS'
BADEXTS: badext badext2
#if no-extraextensions
show traceback for ImportError of hgext.name if devel.debug.extensions is set
$ (hg help help --traceback --debug --config devel.debug.extensions=yes 2>&1) \
> | grep -v '^ ' \
> | filterlog \
> | egrep 'extension..[^p]|^Exception|Traceback|ImportError|^YYYY|not import|ModuleNotFound'
YYYY/MM/DD HH:MM:SS (PID)> loading extensions
YYYY/MM/DD HH:MM:SS (PID)> - processing 5 entries
YYYY/MM/DD HH:MM:SS (PID)> - loading extension: gpg
YYYY/MM/DD HH:MM:SS (PID)> > gpg extension loaded in * (glob)
YYYY/MM/DD HH:MM:SS (PID)> - validating extension tables: gpg
YYYY/MM/DD HH:MM:SS (PID)> - invoking registered callbacks: gpg
YYYY/MM/DD HH:MM:SS (PID)> > callbacks completed in * (glob)
YYYY/MM/DD HH:MM:SS (PID)> - loading extension: badext
*** failed to import extension "badext" from $TESTTMP/badext.py: bit bucket overflow
Traceback (most recent call last):
Exception: bit bucket overflow
YYYY/MM/DD HH:MM:SS (PID)> - loading extension: baddocext
YYYY/MM/DD HH:MM:SS (PID)> > baddocext extension loaded in * (glob)
YYYY/MM/DD HH:MM:SS (PID)> - validating extension tables: baddocext
YYYY/MM/DD HH:MM:SS (PID)> - invoking registered callbacks: baddocext
YYYY/MM/DD HH:MM:SS (PID)> > callbacks completed in * (glob)
YYYY/MM/DD HH:MM:SS (PID)> - loading extension: badext2
YYYY/MM/DD HH:MM:SS (PID)> - could not import hgext.badext2 (No module named *badext2*): trying hgext3rd.badext2 (glob)
Traceback (most recent call last):
ImportError: No module named 'hgext.badext2' (py3 no-py36 !)
ModuleNotFoundError: No module named 'hgext.badext2' (py36 !)
YYYY/MM/DD HH:MM:SS (PID)> - could not import hgext3rd.badext2 (No module named *badext2*): trying badext2 (glob)
Traceback (most recent call last):
ImportError: No module named 'hgext.badext2' (py3 no-py36 !)
ModuleNotFoundError: No module named 'hgext.badext2' (py36 !)
Traceback (most recent call last): (py3 !)
ImportError: No module named 'hgext3rd.badext2' (py3 no-py36 !)
ModuleNotFoundError: No module named 'hgext3rd.badext2' (py36 !)
*** failed to import extension "badext2": No module named 'badext2' (py3 !)
Traceback (most recent call last):
ImportError: No module named 'hgext.badext2' (py3 no-py36 !)
ModuleNotFoundError: No module named 'hgext.badext2' (py36 !)
Traceback (most recent call last): (py3 !)
ImportError: No module named 'hgext3rd.badext2' (py3 no-py36 !)
ModuleNotFoundError: No module named 'hgext3rd.badext2' (py36 !)
Traceback (most recent call last): (py3 !)
ModuleNotFoundError: No module named 'badext2' (py36 !)
ImportError: No module named 'badext2' (py3 no-py36 !)
YYYY/MM/DD HH:MM:SS (PID)> > loaded 2 extensions, total time * (glob)
YYYY/MM/DD HH:MM:SS (PID)> - loading configtable attributes
YYYY/MM/DD HH:MM:SS (PID)> - executing uisetup hooks
YYYY/MM/DD HH:MM:SS (PID)> - running uisetup for gpg
YYYY/MM/DD HH:MM:SS (PID)> > uisetup for gpg took * (glob)
YYYY/MM/DD HH:MM:SS (PID)> - running uisetup for baddocext
YYYY/MM/DD HH:MM:SS (PID)> > uisetup for baddocext took * (glob)
YYYY/MM/DD HH:MM:SS (PID)> > all uisetup took * (glob)
YYYY/MM/DD HH:MM:SS (PID)> - executing extsetup hooks
YYYY/MM/DD HH:MM:SS (PID)> - running extsetup for gpg
YYYY/MM/DD HH:MM:SS (PID)> > extsetup for gpg took * (glob)
YYYY/MM/DD HH:MM:SS (PID)> - running extsetup for baddocext
YYYY/MM/DD HH:MM:SS (PID)> > extsetup for baddocext took * (glob)
YYYY/MM/DD HH:MM:SS (PID)> > all extsetup took * (glob)
YYYY/MM/DD HH:MM:SS (PID)> - executing remaining aftercallbacks
YYYY/MM/DD HH:MM:SS (PID)> > remaining aftercallbacks completed in * (glob)
YYYY/MM/DD HH:MM:SS (PID)> - loading extension registration objects
YYYY/MM/DD HH:MM:SS (PID)> > extension registration object loading took * (glob)
YYYY/MM/DD HH:MM:SS (PID)> > extension baddocext take a total of * to load (glob)
YYYY/MM/DD HH:MM:SS (PID)> > extension gpg take a total of * to load (glob)
YYYY/MM/DD HH:MM:SS (PID)> extension loading complete
#endif
confirm that there's no crash when an extension's documentation is bad
$ hg help --keyword baddocext
*** failed to import extension "badext" from $TESTTMP/badext.py: bit bucket overflow
*** failed to import extension "badext2": No module named 'badext2' (py3 !)
Topics:
extensions Using Additional Features