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
import os
import stat
import sys
from mercurial.node import hex
from mercurial import (
context,
diffutil,
encoding,
hg,
scmutil,
ui as uimod,
)
print_ = print
def print(*args, **kwargs):
"""print() wrapper that flushes stdout buffers to avoid py3 buffer issues
We could also just write directly to sys.stdout.buffer the way the
ui object will, but this was easier for porting the test.
"""
print_(*args, **kwargs)
sys.stdout.flush()
def printb(data, end=b'\n'):
out = getattr(sys.stdout, 'buffer', sys.stdout)
out.write(data + end)
out.flush()
ui = uimod.ui.load()
repo = hg.repository(ui, b'test1', create=1)
os.chdir('test1')
# create 'foo' with fixed time stamp
f = open('foo', 'wb')
f.write(b'foo\n')
f.close()
os.utime('foo', (1000, 1000))
# add+commit 'foo'
repo[None].add([b'foo'])
repo.commit(text=b'commit1', date=b"0 0")
d = repo[None][b'foo'].date()
if os.name == 'nt':
d = d[:2]
print("workingfilectx.date = (%d, %d)" % d)
# test memctx with non-ASCII commit message
def filectxfn(repo, memctx, path):
return context.memfilectx(repo, memctx, b"foo", b"")
ctx = context.memctx(
repo,
[b'tip', None],
encoding.tolocal(b"Gr\xc3\xbcezi!"),
[b"foo"],
filectxfn,
)
ctx.commit()
for enc in "ASCII", "Latin-1", "UTF-8":
encoding.encoding = enc
printb(b"%-8s: %s" % (enc.encode('ascii'), repo[b"tip"].description()))
# test performing a status
def getfilectx(repo, memctx, f):
fctx = memctx.p1()[f]
data, flags = fctx.data(), fctx.flags()
if f == b'foo':
data += b'bar\n'
return context.memfilectx(
repo, memctx, f, data, b'l' in flags, b'x' in flags
)
ctxa = repo[0]
ctxb = context.memctx(
repo,
[ctxa.node(), None],
b"test diff",
[b"foo"],
getfilectx,
ctxa.user(),
ctxa.date(),
)
print(ctxb.status(ctxa))
# test performing a diff on a memctx
diffopts = diffutil.diffallopts(repo.ui, {b'git': True})
for d in ctxb.diff(ctxa, opts=diffopts):
printb(d, end=b'')
# test safeness and correctness of "ctx.status()"
print('= checking context.status():')
# ancestor "wcctx ~ 2"
actx2 = repo[b'.']
repo.wwrite(b'bar-m', b'bar-m\n', b'')
repo.wwrite(b'bar-r', b'bar-r\n', b'')
repo[None].add([b'bar-m', b'bar-r'])
repo.commit(text=b'add bar-m, bar-r', date=b"0 0")
# ancestor "wcctx ~ 1"
actx1 = repo[b'.']
repo.wwrite(b'bar-m', b'bar-m bar-m\n', b'')
repo.wwrite(b'bar-a', b'bar-a\n', b'')
repo[None].add([b'bar-a'])
repo[None].forget([b'bar-r'])
# status at this point:
# M bar-m
# A bar-a
# R bar-r
# C foo
print('== checking workingctx.status:')
wctx = repo[None]
print('wctx._status=%s' % (str(wctx._status)))
print('=== with "pattern match":')
print(
actx1.status(other=wctx, match=scmutil.matchfiles(repo, [b'bar-m', b'foo']))
)
print('wctx._status=%s' % (str(wctx._status)))
print(
actx2.status(other=wctx, match=scmutil.matchfiles(repo, [b'bar-m', b'foo']))
)
print('wctx._status=%s' % (str(wctx._status)))
print('=== with "always match" and "listclean=True":')
print(actx1.status(other=wctx, listclean=True))
print('wctx._status=%s' % (str(wctx._status)))
print(actx2.status(other=wctx, listclean=True))
print('wctx._status=%s' % (str(wctx._status)))
print("== checking workingcommitctx.status:")
wcctx = context.workingcommitctx(
repo,
scmutil.status([b'bar-m'], [b'bar-a'], [], [], [], [], []),
text=b'',
date=b'0 0',
)
print('wcctx._status=%s' % (str(wcctx._status)))
print('=== with "always match":')
print(actx1.status(other=wcctx))
print('wcctx._status=%s' % (str(wcctx._status)))
print(actx2.status(other=wcctx))
print('wcctx._status=%s' % (str(wcctx._status)))
print('=== with "always match" and "listclean=True":')
print(actx1.status(other=wcctx, listclean=True))
print('wcctx._status=%s' % (str(wcctx._status)))
print(actx2.status(other=wcctx, listclean=True))
print('wcctx._status=%s' % (str(wcctx._status)))
print('=== with "pattern match":')
print(
actx1.status(
other=wcctx, match=scmutil.matchfiles(repo, [b'bar-m', b'foo'])
)
)
print('wcctx._status=%s' % (str(wcctx._status)))
print(
actx2.status(
other=wcctx, match=scmutil.matchfiles(repo, [b'bar-m', b'foo'])
)
)
print('wcctx._status=%s' % (str(wcctx._status)))
print('=== with "pattern match" and "listclean=True":')
print(
actx1.status(
other=wcctx,
match=scmutil.matchfiles(repo, [b'bar-r', b'foo']),
listclean=True,
)
)
print('wcctx._status=%s' % (str(wcctx._status)))
print(
actx2.status(
other=wcctx,
match=scmutil.matchfiles(repo, [b'bar-r', b'foo']),
listclean=True,
)
)
print('wcctx._status=%s' % (str(wcctx._status)))
os.chdir('..')
# test manifestlog being changed
print('== commit with manifestlog invalidated')
repo = hg.repository(ui, b'test2', create=1)
os.chdir('test2')
# make some commits
for i in [b'1', b'2', b'3']:
with open(i, 'wb') as f:
f.write(i)
status = scmutil.status([], [i], [], [], [], [], [])
ctx = context.workingcommitctx(
repo, status, text=i, user=b'test@test.com', date=(0, 0)
)
ctx.p1().manifest() # side effect: cache manifestctx
n = repo.commitctx(ctx)
printb(b'commit %s: %s' % (i, hex(n)))
# touch 00manifest.i mtime so storecache could expire.
# repo.__dict__['manifestlog'] is deleted by transaction releasefn.
st = repo.svfs.stat(b'00manifest.i')
repo.svfs.utime(
b'00manifest.i', (st[stat.ST_MTIME] + 1, st[stat.ST_MTIME] + 1)
)
# read the file just committed
try:
if repo[n][i].data() != i:
print('data mismatch')
except Exception as ex:
print('cannot read data: %r' % ex)
with repo.wlock(), repo.lock(), repo.transaction(b'test'):
with open(b'4', 'wb') as f:
f.write(b'4')
repo.dirstate.set_tracked(b'4')
repo.commit(b'4')
revsbefore = len(repo.changelog)
repo.invalidate(clearfilecache=True)
revsafter = len(repo.changelog)
if revsbefore != revsafter:
print('changeset lost by repo.invalidate()')