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 python
"""This does HTTP GET requests given a host:port and path and returns
a subset of the headers plus the body of the result."""
import argparse
import json
import os
import sys
from mercurial import (
pycompat,
util,
)
httplib = util.httplib
try:
import msvcrt
msvcrt.setmode(sys.stdout.fileno(), os.O_BINARY)
msvcrt.setmode(sys.stderr.fileno(), os.O_BINARY)
except ImportError:
pass
stdout = getattr(sys.stdout, 'buffer', sys.stdout)
parser = argparse.ArgumentParser()
parser.add_argument('--twice', action='store_true')
parser.add_argument('--headeronly', action='store_true')
parser.add_argument('--json', action='store_true')
parser.add_argument('--hgproto')
parser.add_argument(
'--requestheader',
nargs='*',
default=[],
help='Send an additional HTTP request header. Argument '
'value is <header>=<value>',
)
parser.add_argument('--bodyfile', help='Write HTTP response body to a file')
parser.add_argument('host')
parser.add_argument('path')
parser.add_argument('show', nargs='*')
args = parser.parse_args()
twice = args.twice
headeronly = args.headeronly
formatjson = args.json
hgproto = args.hgproto
requestheaders = args.requestheader
tag = None
def request(host, path, show):
assert not path.startswith('/'), path
global tag
headers = {}
if tag:
headers['If-None-Match'] = tag
if hgproto:
headers['X-HgProto-1'] = hgproto
for header in requestheaders:
key, value = header.split('=', 1)
headers[key] = value
conn = httplib.HTTPConnection(host)
conn.request("GET", '/' + path, None, headers)
response = conn.getresponse()
stdout.write(
b'%d %s\n' % (response.status, response.reason.encode('ascii'))
)
if show[:1] == ['-']:
show = sorted(
h for h, v in response.getheaders() if h.lower() not in show
)
for h in [h.lower() for h in show]:
if response.getheader(h, None) is not None:
stdout.write(
b"%s: %s\n"
% (h.encode('ascii'), response.getheader(h).encode('ascii'))
)
if headeronly:
# still read the body to prevent windows to be unhappy about that
# (this might some flakyness in test-hgweb-filelog.t on Windows)
data = response.read()
else:
stdout.write(b'\n')
data = response.read()
if args.bodyfile:
bodyfh = open(args.bodyfile, 'wb')
else:
bodyfh = stdout
# Pretty print JSON. This also has the beneficial side-effect
# of verifying emitted JSON is well-formed.
if formatjson:
# json.dumps() will print trailing newlines. Eliminate them
# to make tests easier to write.
data = pycompat.json_loads(data)
lines = json.dumps(data, sort_keys=True, indent=2).splitlines()
for line in lines:
bodyfh.write(pycompat.sysbytes(line.rstrip()))
bodyfh.write(b'\n')
else:
bodyfh.write(data)
if args.bodyfile:
bodyfh.close()
if twice and response.getheader('ETag', None):
tag = response.getheader('ETag')
# further try to please the windows-flakyness deity
conn.close()
return response.status
status = request(args.host, args.path, args.show)
if twice:
status = request(args.host, args.path, args.show)
if 200 <= status <= 305:
sys.exit(0)
sys.exit(1)