sparse-revlog: implement algorithm to write sparse delta chains (
issue5480)
The classic behavior of revlog._isgooddeltainfo is to consider the span size
of the whole delta chain, and limit it to 4 * textlen.
Once sparse-revlog writing is allowed (and enforced with a requirement),
revlog._isgooddeltainfo considers the span of the largest chunk as the
distance used in the verification, instead of using the span of the whole
delta chain.
In order to compute the span of the largest chunk, we need to slice into
chunks a chain with the new revision at the top of the revlog, and take the
maximal span of these chunks. The sparse read density is a parameter to the
slicing, as it will stop when the global read density reaches this threshold.
For instance, a density of 50% means that 2 of 4 read bytes are actually used
for the reconstruction of the revision (the others are part of other chains).
This allows a new revision to be potentially stored with a diff against
another revision anywhere in the history, instead of forcing it in the last 4
* textlen. The result is a much better compression on repositories that have
many concurrent branches. Here are a comparison between using deltas from
current upstream (aggressive-merge-deltas on by default) and deltas from a
sparse-revlog
Comparison of `.hg/store/` size:
mercurial (6.74% merges):
before: 46,831,873 bytes
after: 46,795,992 bytes (no relevant change)
pypy (8.30% merges):
before: 333,524,651 bytes
after: 308,417,511 bytes -8%
netbeans (34.21% merges):
before: 1,141,847,554 bytes
after: 1,131,093,161 bytes -1%
mozilla-central (4.84% merges):
before: 2,344,248,850 bytes
after: 2,328,459,258 bytes -1%
large-private-repo-A (merge 19.73%)
before: 41,510,550,163 bytes
after: 8,121,763,428 bytes -80%
large-private-repo-B (23.77%)
before: 58,702,221,709 bytes
after: 8,351,588,828 bytes -76%
Comparison of `00manifest.d` size:
mercurial (6.74% merges):
before: 6,143,044 bytes
after: 6,107,163 bytes
pypy (8.30% merges):
before: 52,941,780 bytes
after: 27,834,082 bytes -48%
netbeans (34.21% merges):
before: 130,088,982 bytes
after: 119,337,636 bytes -10%
mozilla-central (4.84% merges):
before: 215,096,339 bytes
after: 199,496,863 bytes -8%
large-private-repo-A (merge 19.73%)
before: 33,725,285,081 bytes
after: 390,302,545 bytes -99%
large-private-repo-B (23.77%)
before: 49,457,701,645 bytes
after: 1,366,752,187 bytes -97%
The better delta chains provide a performance boost in relevant repositories:
pypy, bundling 1000 revisions:
before: 1.670s
after: 1.149s -31%
Unbundling got a bit slower. probably because the sparse algorithm is still
pure
python.
pypy, unbundling 1000 revisions:
before: 4.062s
after: 4.507s +10%
Performance of bundle/unbundle in repository with few concurrent branches (eg:
mercurial) are unaffected.
No significant differences have been noticed then timing `hg push` and `hg
pull` locally. More state timings are being gathered.
Same as for aggressive-merge-delta, better delta comes with longer delta
chains. Longer chains have a performance impact. For example. The length of
the chain needed to get the manifest of pypy's tip moves from 82 item to 1929
items. This moves the restore time from 3.88ms to 11.3ms.
Delta chain length is an independent issue that affects repository without
this changes. It will be dealt with independently.
No significant differences have been observed on repositories where
`sparse-revlog` have not much effect (mercurial, unity, netbeans). On pypy,
small differences have been observed on some operation affected by delta chain
building and retrieval.
pypy, perfmanifest
before: 0.006162s
after: 0.017899s +190%
pypy, commit:
before: 0.382
after: 0.376 -1%
pypy, status:
before: 0.157
after: 0.168 +7%
More comprehensive and stable timing comparisons are in progress.
setup repo
$ hg init t
$ cd t
$ echo a > a
$ hg commit -Am'add a'
adding a
$ hg verify
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
1 files, 1 changesets, 1 total revisions
$ hg parents
changeset: 0:1f0dee641bb7
tag: tip
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: add a
rollback to null revision
$ hg status
$ hg rollback
repository tip rolled back to revision -1 (undo commit)
working directory now based on revision -1
$ hg verify
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
0 files, 0 changesets, 0 total revisions
$ hg parents
$ hg status
A a
Two changesets this time so we rollback to a real changeset
$ hg commit -m'add a again'
$ echo a >> a
$ hg commit -m'modify a'
Test issue 902 (current branch is preserved)
$ hg branch test
marked working directory as branch test
(branches are permanent and global, did you want a bookmark?)
$ hg rollback
repository tip rolled back to revision 0 (undo commit)
working directory now based on revision 0
$ hg branch
default
Test issue 1635 (commit message saved)
$ cat .hg/last-message.txt ; echo
modify a
Test rollback of hg before issue 902 was fixed
$ hg commit -m "test3"
$ hg branch test
marked working directory as branch test
(branches are permanent and global, did you want a bookmark?)
$ rm .hg/undo.branch
$ hg rollback
repository tip rolled back to revision 0 (undo commit)
named branch could not be reset: current branch is still 'test'
working directory now based on revision 0
$ hg branch
test
working dir unaffected by rollback: do not restore dirstate et. al.
$ hg log --template '{rev} {branch} {desc|firstline}\n'
0 default add a again
$ hg status
M a
$ hg bookmark foo
$ hg commit -m'modify a again'
$ echo b > b
$ hg bookmark bar -r default #making bar active, before the transaction
$ hg commit -Am'add b'
adding b
$ hg log --template '{rev} {branch} {desc|firstline}\n'
2 test add b
1 test modify a again
0 default add a again
$ hg update bar
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
(activating bookmark bar)
$ cat .hg/undo.branch ; echo
test
$ hg rollback -f
repository tip rolled back to revision 1 (undo commit)
$ hg id -n
0
$ hg branch
default
$ cat .hg/bookmarks.current ; echo
bar
$ hg bookmark --delete foo bar
rollback by pretxncommit saves commit message (issue1635)
$ echo a >> a
$ hg --config hooks.pretxncommit=false commit -m"precious commit message"
transaction abort!
rollback completed
abort: pretxncommit hook exited with status * (glob)
[255]
$ cat .hg/last-message.txt ; echo
precious commit message
same thing, but run $EDITOR
$ cat > editor.sh << '__EOF__'
> echo "another precious commit message" > "$1"
> __EOF__
$ HGEDITOR="\"sh\" \"`pwd`/editor.sh\"" hg --config hooks.pretxncommit=false commit 2>&1
note: commit message saved in .hg/last-message.txt
transaction abort!
rollback completed
abort: pretxncommit hook exited with status * (glob)
[255]
$ cat .hg/last-message.txt
another precious commit message
test rollback on served repository
#if serve
$ hg commit -m "precious commit message"
$ hg serve -p $HGPORT -d --pid-file=hg.pid -A access.log -E errors.log
$ cat hg.pid >> $DAEMON_PIDS
$ cd ..
$ hg clone http://localhost:$HGPORT u
requesting all changes
adding changesets
adding manifests
adding file changes
added 3 changesets with 2 changes to 1 files (+1 heads)
new changesets 23b0221f3370:068774709090
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cd u
$ hg id default
068774709090
now rollback and observe that 'hg serve' reloads the repository and
presents the correct tip changeset:
$ hg -R ../t rollback
repository tip rolled back to revision 1 (undo commit)
working directory now based on revision 0
$ hg id default
791dd2169706
$ killdaemons.py
#endif
update to older changeset and then refuse rollback, because
that would lose data (issue2998)
$ cd ../t
$ hg -q update
$ rm `hg status -un`
$ template='{rev}:{node|short} [{branch}] {desc|firstline}\n'
$ echo 'valuable new file' > b
$ echo 'valuable modification' >> a
$ hg commit -A -m'a valuable change'
adding b
$ hg update 0
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ hg rollback
abort: rollback of last commit while not checked out may lose data
(use -f to force)
[255]
$ hg tip -q
2:4d9cd3795eea
$ hg rollback -f
repository tip rolled back to revision 1 (undo commit)
$ hg status
$ hg log --removed b # yep, it's gone
same again, but emulate an old client that doesn't write undo.desc
$ hg -q update
$ echo 'valuable modification redux' >> a
$ hg commit -m'a valuable change redux'
$ rm .hg/undo.desc
$ hg update 0
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg rollback
rolling back unknown transaction
$ cat a
a
corrupt journal test
$ echo "foo" > .hg/store/journal
$ hg recover
rolling back interrupted transaction
couldn't read journal entry 'foo\n'!
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
1 files, 2 changesets, 2 total revisions
rollback disabled by config
$ cat >> $HGRCPATH <<EOF
> [ui]
> rollback = false
> EOF
$ echo narf >> pinky-sayings.txt
$ hg add pinky-sayings.txt
$ hg ci -m 'First one.'
$ hg rollback
abort: rollback is disabled because it is unsafe
(see `hg help -v rollback` for information)
[255]
$ cd ..
I/O errors on stdio are handled properly (issue5658)
$ cat > badui.py << EOF
> import errno
> from mercurial.i18n import _
> from mercurial import (
> error,
> registrar,
> ui as uimod,
> )
>
> configtable = {}
> configitem = registrar.configitem(configtable)
>
> configitem(b'ui', b'ioerrors',
> default=list,
> )
>
> def pretxncommit(ui, repo, **kwargs):
> ui.warn(b'warn during pretxncommit\n')
>
> def pretxnclose(ui, repo, **kwargs):
> ui.warn(b'warn during pretxnclose\n')
>
> def txnclose(ui, repo, **kwargs):
> ui.warn(b'warn during txnclose\n')
>
> def txnabort(ui, repo, **kwargs):
> ui.warn(b'warn during abort\n')
>
> class fdproxy(object):
> def __init__(self, ui, o):
> self._ui = ui
> self._o = o
>
> def __getattr__(self, attr):
> return getattr(self._o, attr)
>
> def write(self, msg):
> errors = set(self._ui.configlist(b'ui', b'ioerrors'))
> pretxncommit = msg == b'warn during pretxncommit\n'
> pretxnclose = msg == b'warn during pretxnclose\n'
> txnclose = msg == b'warn during txnclose\n'
> txnabort = msg == b'warn during abort\n'
> msgabort = msg == _(b'transaction abort!\n')
> msgrollback = msg == _(b'rollback completed\n')
>
> if pretxncommit and b'pretxncommit' in errors:
> raise IOError(errno.EPIPE, 'simulated epipe')
> if pretxnclose and b'pretxnclose' in errors:
> raise IOError(errno.EIO, 'simulated eio')
> if txnclose and b'txnclose' in errors:
> raise IOError(errno.EBADF, 'simulated badf')
> if txnabort and b'txnabort' in errors:
> raise IOError(errno.EPIPE, 'simulated epipe')
> if msgabort and b'msgabort' in errors:
> raise IOError(errno.EBADF, 'simulated ebadf')
> if msgrollback and b'msgrollback' in errors:
> raise IOError(errno.EIO, 'simulated eio')
>
> return self._o.write(msg)
>
> def uisetup(ui):
> class badui(ui.__class__):
> def write_err(self, *args, **kwargs):
> olderr = self.ferr
> try:
> self.ferr = fdproxy(self, olderr)
> return super(badui, self).write_err(*args, **kwargs)
> finally:
> self.ferr = olderr
>
> ui.__class__ = badui
>
> def reposetup(ui, repo):
> ui.setconfig(b'hooks', b'pretxnclose.badui', pretxnclose, b'badui')
> ui.setconfig(b'hooks', b'txnclose.badui', txnclose, b'badui')
> ui.setconfig(b'hooks', b'pretxncommit.badui', pretxncommit, b'badui')
> ui.setconfig(b'hooks', b'txnabort.badui', txnabort, b'badui')
> EOF
$ cat >> $HGRCPATH << EOF
> [extensions]
> badui = $TESTTMP/badui.py
> EOF
An I/O error during pretxncommit is handled
$ hg init ioerror-pretxncommit
$ cd ioerror-pretxncommit
$ echo 0 > foo
$ hg -q commit -A -m initial
warn during pretxncommit
warn during pretxnclose
warn during txnclose
$ echo 1 > foo
$ hg --config ui.ioerrors=pretxncommit commit -m 'error during pretxncommit'
warn during pretxnclose
warn during txnclose
$ hg commit -m 'commit 1'
nothing changed
[1]
$ cd ..
An I/O error during pretxnclose is handled
$ hg init ioerror-pretxnclose
$ cd ioerror-pretxnclose
$ echo 0 > foo
$ hg -q commit -A -m initial
warn during pretxncommit
warn during pretxnclose
warn during txnclose
$ echo 1 > foo
$ hg --config ui.ioerrors=pretxnclose commit -m 'error during pretxnclose'
warn during pretxncommit
warn during txnclose
$ hg commit -m 'commit 1'
nothing changed
[1]
$ cd ..
An I/O error during txnclose is handled
$ hg init ioerror-txnclose
$ cd ioerror-txnclose
$ echo 0 > foo
$ hg -q commit -A -m initial
warn during pretxncommit
warn during pretxnclose
warn during txnclose
$ echo 1 > foo
$ hg --config ui.ioerrors=txnclose commit -m 'error during txnclose'
warn during pretxncommit
warn during pretxnclose
$ hg commit -m 'commit 1'
nothing changed
[1]
$ cd ..
An I/O error writing "transaction abort" is handled
$ hg init ioerror-msgabort
$ cd ioerror-msgabort
$ echo 0 > foo
$ hg -q commit -A -m initial
warn during pretxncommit
warn during pretxnclose
warn during txnclose
$ echo 1 > foo
$ hg --config ui.ioerrors=msgabort --config hooks.pretxncommit=false commit -m 'error during abort message'
warn during abort
rollback completed
abort: pretxncommit hook exited with status 1
[255]
$ hg commit -m 'commit 1'
warn during pretxncommit
warn during pretxnclose
warn during txnclose
$ cd ..
An I/O error during txnabort should still result in rollback
$ hg init ioerror-txnabort
$ cd ioerror-txnabort
$ echo 0 > foo
$ hg -q commit -A -m initial
warn during pretxncommit
warn during pretxnclose
warn during txnclose
$ echo 1 > foo
$ hg --config ui.ioerrors=txnabort --config hooks.pretxncommit=false commit -m 'error during abort'
transaction abort!
rollback completed
abort: pretxncommit hook exited with status 1
[255]
$ hg commit -m 'commit 1'
warn during pretxncommit
warn during pretxnclose
warn during txnclose
$ cd ..
An I/O error writing "rollback completed" is handled
$ hg init ioerror-msgrollback
$ cd ioerror-msgrollback
$ echo 0 > foo
$ hg -q commit -A -m initial
warn during pretxncommit
warn during pretxnclose
warn during txnclose
$ echo 1 > foo
$ hg --config ui.ioerrors=msgrollback --config hooks.pretxncommit=false commit -m 'error during rollback message'
transaction abort!
warn during abort
abort: pretxncommit hook exited with status 1
[255]
$ hg verify
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
1 files, 1 changesets, 1 total revisions
$ cd ..
Multiple I/O errors after transaction open are handled.
This is effectively what happens if a peer disconnects in the middle
of a transaction.
$ hg init ioerror-multiple
$ cd ioerror-multiple
$ echo 0 > foo
$ hg -q commit -A -m initial
warn during pretxncommit
warn during pretxnclose
warn during txnclose
$ echo 1 > foo
$ hg --config ui.ioerrors=pretxncommit,pretxnclose,txnclose,txnabort,msgabort,msgrollback commit -m 'multiple errors'
$ hg verify
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
1 files, 2 changesets, 2 total revisions
$ cd ..