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
# test-batching.py - tests for transparent command batching
#
# Copyright 2011 Peter Arrenbrecht <peter@arrenbrecht.ch>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
import contextlib
from mercurial import (
localrepo,
pycompat,
wireprotov1peer,
)
def bprint(*bs):
print(*[pycompat.sysstr(b) for b in bs])
# equivalent of repo.repository
class thing:
def hello(self):
return b"Ready."
# equivalent of localrepo.localrepository
class localthing(thing):
def foo(self, one, two=None):
if one:
return b"%s and %s" % (
one,
two,
)
return b"Nope"
def bar(self, b, a):
return b"%s und %s" % (
b,
a,
)
def greet(self, name=None):
return b"Hello, %s" % name
@contextlib.contextmanager
def commandexecutor(self):
e = localrepo.localcommandexecutor(self)
try:
yield e
finally:
e.close()
# usage of "thing" interface
def use(it):
# Direct call to base method shared between client and server.
bprint(it.hello())
# Direct calls to proxied methods. They cause individual roundtrips.
bprint(it.foo(b"Un", two=b"Deux"))
bprint(it.bar(b"Eins", b"Zwei"))
# Batched call to a couple of proxied methods.
with it.commandexecutor() as e:
ffoo = e.callcommand(b'foo', {b'one': b'One', b'two': b'Two'})
fbar = e.callcommand(b'bar', {b'b': b'Eins', b'a': b'Zwei'})
fbar2 = e.callcommand(b'bar', {b'b': b'Uno', b'a': b'Due'})
bprint(ffoo.result())
bprint(fbar.result())
bprint(fbar2.result())
# local usage
mylocal = localthing()
print()
bprint(b"== Local")
use(mylocal)
# demo remoting; mimicks what wireproto and HTTP/SSH do
# shared
def escapearg(plain):
return (
plain.replace(b':', b'::')
.replace(b',', b':,')
.replace(b';', b':;')
.replace(b'=', b':=')
)
def unescapearg(escaped):
return (
escaped.replace(b':=', b'=')
.replace(b':;', b';')
.replace(b':,', b',')
.replace(b'::', b':')
)
# server side
# equivalent of wireproto's global functions
class server:
def __init__(self, local):
self.local = local
def _call(self, name, args):
args = dict(arg.split(b'=', 1) for arg in args)
return getattr(self, name)(**args)
def perform(self, req):
bprint(b"REQ:", req)
name, args = req.split(b'?', 1)
args = args.split(b'&')
vals = dict(arg.split(b'=', 1) for arg in args)
res = getattr(self, pycompat.sysstr(name))(**pycompat.strkwargs(vals))
bprint(b" ->", res)
return res
def batch(self, cmds):
res = []
for pair in cmds.split(b';'):
name, args = pair.split(b':', 1)
vals = {}
for a in args.split(b','):
if a:
n, v = a.split(b'=')
vals[n] = unescapearg(v)
res.append(
escapearg(
getattr(self, pycompat.sysstr(name))(
**pycompat.strkwargs(vals)
)
)
)
return b';'.join(res)
def foo(self, one, two):
return mangle(self.local.foo(unmangle(one), unmangle(two)))
def bar(self, b, a):
return mangle(self.local.bar(unmangle(b), unmangle(a)))
def greet(self, name):
return mangle(self.local.greet(unmangle(name)))
myserver = server(mylocal)
# local side
# equivalent of wireproto.encode/decodelist, that is, type-specific marshalling
# here we just transform the strings a bit to check we're properly en-/decoding
def mangle(s):
return b''.join(pycompat.bytechr(ord(c) + 1) for c in pycompat.bytestr(s))
def unmangle(s):
return b''.join(pycompat.bytechr(ord(c) - 1) for c in pycompat.bytestr(s))
# equivalent of wireproto.wirerepository and something like http's wire format
class remotething(thing):
def __init__(self, server):
self.server = server
def _submitone(self, name, args):
req = name + b'?' + b'&'.join([b'%s=%s' % (n, v) for n, v in args])
return self.server.perform(req)
def _submitbatch(self, cmds):
req = []
for name, args in cmds:
args = b','.join(n + b'=' + escapearg(v) for n, v in args)
req.append(name + b':' + args)
req = b';'.join(req)
res = self._submitone(
b'batch',
[
(
b'cmds',
req,
)
],
)
for r in res.split(b';'):
yield r
@contextlib.contextmanager
def commandexecutor(self):
e = wireprotov1peer.peerexecutor(self)
try:
yield e
finally:
e.close()
@wireprotov1peer.batchable
def foo(self, one, two=None):
encoded_args = [
(
b'one',
mangle(one),
),
(
b'two',
mangle(two),
),
]
return encoded_args, unmangle
@wireprotov1peer.batchable
def bar(self, b, a):
return [
(
b'b',
mangle(b),
),
(
b'a',
mangle(a),
),
], unmangle
# greet is coded directly. It therefore does not support batching. If it
# does appear in a batch, the batch is split around greet, and the call to
# greet is done in its own roundtrip.
def greet(self, name=None):
return unmangle(
self._submitone(
b'greet',
[
(
b'name',
mangle(name),
)
],
)
)
# demo remote usage
myproxy = remotething(myserver)
print()
bprint(b"== Remote")
use(myproxy)