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
#!/usr/bin/env python3
#
# A small script to automatically reject idle Diffs
#
# you need to set the PHABBOT_USER and PHABBOT_TOKEN environment variable for authentication
import datetime
import os
import sys
import phabricator
MESSAGE = """There seems to have been no activities on this Diff for the past 3 Months.
By policy, we are automatically moving it out of the `need-review` state.
Please, move it back to `need-review` without hesitation if this diff should still be discussed.
:baymax:need-review-idle:
"""
PHAB_URL = "https://phab.mercurial-scm.org/api/"
USER = os.environ.get("PHABBOT_USER", "baymax")
TOKEN = os.environ.get("PHABBOT_TOKEN")
NOW = datetime.datetime.now()
# 3 months in seconds
DELAY = 60 * 60 * 24 * 30 * 3
def get_all_diff(phab):
"""Fetch all the diff that the need review"""
return phab.differential.query(
status="status-needs-review",
order="order-modified",
paths=[('HG', None)],
)
def filter_diffs(diffs, older_than):
"""filter diffs to only keep the one unmodified sin <older_than> seconds"""
olds = []
for d in diffs:
modified = int(d['dateModified'])
modified = datetime.datetime.fromtimestamp(modified)
d["idleFor"] = idle_for = NOW - modified
if idle_for.total_seconds() > older_than:
olds.append(d)
return olds
def nudge_diff(phab, diff):
"""Comment on the idle diff and reject it"""
diff_id = int(d['id'])
phab.differential.createcomment(
revision_id=diff_id, message=MESSAGE, action="reject"
)
if not USER:
print(
"not user specified please set PHABBOT_USER and PHABBOT_TOKEN",
file=sys.stderr,
)
elif not TOKEN:
print(
"not api-token specified please set PHABBOT_USER and PHABBOT_TOKEN",
file=sys.stderr,
)
sys.exit(1)
phab = phabricator.Phabricator(USER, host=PHAB_URL, token=TOKEN)
phab.connect()
phab.update_interfaces()
print('Hello "%s".' % phab.user.whoami()['realName'])
diffs = get_all_diff(phab)
print("Found %d Diffs" % len(diffs))
olds = filter_diffs(diffs, DELAY)
print("Found %d old Diffs" % len(olds))
for d in olds:
diff_id = d['id']
status = d['statusName']
modified = int(d['dateModified'])
idle_for = d["idleFor"]
msg = 'nudging D%s in "%s" state for %s'
print(msg % (diff_id, status, idle_for))
# uncomment to actually affect phab
nudge_diff(phab, d)