commit: improve the files field of changelog for merges
Currently, the files list of merge commits repeats all the deletions
(either actual deletions, or files that got renamed) that happened
between base and p2 of the merge. If p2 is the main branch, the list
can easily be much bigger than the change being merged.
This results in various problems worth improving:
- changelog is bigger than necessary
- `hg log directory` lists many unrelated merge commits, and `hg log
-v -r commit` frequently fills multiple screens worth of files
- it possibly slows down adjustlinkrev, by forcing it to read more
manifests, and that function can certainly be a bottleneck
- the server side of pulls can waste a lot of time simply opening the
filelogs for pointless files (the constant factors for opening even
a tiny filelog is apparently pretty bad)
So stop listing such files as described in the code. Impacted merge
commits and their descendants get a different hash than they would
have without this. This doesn't seem problematic, except for
convert. The previous commit helped with that in the hg->hg case (but
if you do svn->hg twice from scratch, hashes can still change).
The rest of the description is numbers. I don't have much to report,
because recreating the files list of existing repositories is not
easy:
- debugupgradeformat and bundle/unbundle don't recreate the list
- export/import tends to choke quickly applying patches or on
description that contain diffs,
- merge commits from the convert extension don't have the right files
list for reasons orthogonal to the current commit
- replaying the merge with hg update/hg merge/hg revert --all/hg
commit can end up failing in hg revert
- I wasn't sure that using debugsetparents + debugrebuilddirstate
would really build the right thing
I measured commit time before and after this change, in a case with no
files filtered out, several files filtered out (no difference) and 5k
files filtered out (+1% time).
Recreating the 100 more recent merges in a private repo, the
concatenated uncompressed files lists goes from 1.12MB to
0.52MB. Excluding 3 merges that are not representative, then the size
goes from 570k to 15k.
I converted part of mozilla-central, and observed file list shrinking
quite a bit too, starting at the very first merge,
733641d9feaf, going
from 550 files to 10 files (although they have relatively few merges,
so they probably wouldn't care).
Differential Revision: https://phab.mercurial-scm.org/D6613
revlog.parseindex must be able to parse the index file even if
an index entry is split between two 64k blocks. The ideal test
would be to create an index file with inline data where
64k < size < 64k + 64 (64k is the size of the read buffer, 64 is
the size of an index entry) and with an index entry starting right
before the 64k block boundary, and try to read it.
We approximate that by reducing the read buffer to 1 byte.
$ hg init a
$ cd a
$ echo abc > foo
$ hg add foo
$ hg commit -m 'add foo'
$ echo >> foo
$ hg commit -m 'change foo'
$ hg log -r 0:
changeset: 0:7c31755bf9b5
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: add foo
changeset: 1:26333235a41c
tag: tip
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: change foo
$ cat >> test.py << EOF
> from __future__ import print_function
> from mercurial import changelog, node, pycompat, vfs
>
> class singlebyteread(object):
> def __init__(self, real):
> self.real = real
>
> def read(self, size=-1):
> if size == 65536:
> size = 1
> return self.real.read(size)
>
> def __getattr__(self, key):
> return getattr(self.real, key)
>
> def __enter__(self):
> self.real.__enter__()
> return self
>
> def __exit__(self, *args, **kwargs):
> return self.real.__exit__(*args, **kwargs)
>
> def opener(*args):
> o = vfs.vfs(*args)
> def wrapper(*a, **kwargs):
> f = o(*a, **kwargs)
> return singlebyteread(f)
> return wrapper
>
> cl = changelog.changelog(opener(b'.hg/store'))
> print(len(cl), 'revisions:')
> for r in cl:
> print(pycompat.sysstr(node.short(cl.node(r))))
> EOF
$ "$PYTHON" test.py
2 revisions:
7c31755bf9b5
26333235a41c
$ cd ..
#if no-pure
Test SEGV caused by bad revision passed to reachableroots() (issue4775):
$ cd a
$ "$PYTHON" <<EOF
> from __future__ import print_function
> from mercurial import changelog, vfs
> cl = changelog.changelog(vfs.vfs(b'.hg/store'))
> print('good heads:')
> for head in [0, len(cl) - 1, -1]:
> print('%s: %r' % (head, cl.reachableroots(0, [head], [0])))
> print('bad heads:')
> for head in [len(cl), 10000, -2, -10000, None]:
> print('%s:' % head, end=' ')
> try:
> cl.reachableroots(0, [head], [0])
> print('uncaught buffer overflow?')
> except (IndexError, TypeError) as inst:
> print(inst)
> print('good roots:')
> for root in [0, len(cl) - 1, -1]:
> print('%s: %r' % (root, cl.reachableroots(root, [len(cl) - 1], [root])))
> print('out-of-range roots are ignored:')
> for root in [len(cl), 10000, -2, -10000]:
> print('%s: %r' % (root, cl.reachableroots(root, [len(cl) - 1], [root])))
> print('bad roots:')
> for root in [None]:
> print('%s:' % root, end=' ')
> try:
> cl.reachableroots(root, [len(cl) - 1], [root])
> print('uncaught error?')
> except TypeError as inst:
> print(inst)
> EOF
good heads:
0: [0]
1: [0]
-1: []
bad heads:
2: head out of range
10000: head out of range
-2: head out of range
-10000: head out of range
None: an integer is required( .got type NoneType.)? (re)
good roots:
0: [0]
1: [1]
-1: [-1]
out-of-range roots are ignored:
2: []
10000: []
-2: []
-10000: []
bad roots:
None: an integer is required( .got type NoneType.)? (re)
$ cd ..
Test corrupted p1/p2 fields that could cause SEGV at parsers.c:
$ mkdir invalidparent
$ cd invalidparent
$ hg clone --pull -q --config phases.publish=False ../a limit --config format.sparse-revlog=no
$ hg clone --pull -q --config phases.publish=False ../a neglimit --config format.sparse-revlog=no
$ hg clone --pull -q --config phases.publish=False ../a segv --config format.sparse-revlog=no
$ rm -R limit/.hg/cache neglimit/.hg/cache segv/.hg/cache
$ "$PYTHON" <<EOF
> data = open("limit/.hg/store/00changelog.i", "rb").read()
> poisons = [
> (b'limit', b'\0\0\0\x02'),
> (b'neglimit', b'\xff\xff\xff\xfe'),
> (b'segv', b'\0\x01\0\0'),
> ]
> for n, p in poisons:
> # corrupt p1 at rev0 and p2 at rev1
> d = data[:24] + p + data[28:127 + 28] + p + data[127 + 32:]
> open(n + b"/.hg/store/00changelog.i", "wb").write(d)
> EOF
$ hg -R limit debugrevlogindex -f1 -c
rev flag size link p1 p2 nodeid
0 0000 62 0 2 -1 7c31755bf9b5
1 0000 65 1 0 2 26333235a41c
$ hg -R limit debugdeltachain -c
rev chain# chainlen prev delta size rawsize chainsize ratio lindist extradist extraratio
0 1 1 -1 base 63 62 63 1.01613 63 0 0.00000
1 2 1 -1 base 66 65 66 1.01538 66 0 0.00000
$ hg -R neglimit debugrevlogindex -f1 -c
rev flag size link p1 p2 nodeid
0 0000 62 0 -2 -1 7c31755bf9b5
1 0000 65 1 0 -2 26333235a41c
$ hg -R segv debugrevlogindex -f1 -c
rev flag size link p1 p2 nodeid
0 0000 62 0 65536 -1 7c31755bf9b5
1 0000 65 1 0 65536 26333235a41c
$ hg -R segv debugdeltachain -c
rev chain# chainlen prev delta size rawsize chainsize ratio lindist extradist extraratio
0 1 1 -1 base 63 62 63 1.01613 63 0 0.00000
1 2 1 -1 base 66 65 66 1.01538 66 0 0.00000
$ cat <<EOF > test.py
> from __future__ import print_function
> import sys
> from mercurial import changelog, pycompat, vfs
> cl = changelog.changelog(vfs.vfs(pycompat.fsencode(sys.argv[1])))
> n0, n1 = cl.node(0), cl.node(1)
> ops = [
> ('reachableroots',
> lambda: cl.index.reachableroots2(0, [1], [0], False)),
> ('compute_phases_map_sets', lambda: cl.computephases([[0], []])),
> ('index_headrevs', lambda: cl.headrevs()),
> ('find_gca_candidates', lambda: cl.commonancestorsheads(n0, n1)),
> ('find_deepest', lambda: cl.ancestor(n0, n1)),
> ]
> for l, f in ops:
> print(l + ':', end=' ')
> try:
> f()
> print('uncaught buffer overflow?')
> except ValueError as inst:
> print(inst)
> EOF
$ "$PYTHON" test.py limit/.hg/store
reachableroots: parent out of range
compute_phases_map_sets: parent out of range
index_headrevs: parent out of range
find_gca_candidates: parent out of range
find_deepest: parent out of range
$ "$PYTHON" test.py neglimit/.hg/store
reachableroots: parent out of range
compute_phases_map_sets: parent out of range
index_headrevs: parent out of range
find_gca_candidates: parent out of range
find_deepest: parent out of range
$ "$PYTHON" test.py segv/.hg/store
reachableroots: parent out of range
compute_phases_map_sets: parent out of range
index_headrevs: parent out of range
find_gca_candidates: parent out of range
find_deepest: parent out of range
$ cd ..
#endif