view tests/test-mq-qpush-fail.t @ 30155:b7a966ce89ed

changelog: disable delta chains

This patch disables delta chains on changelogs. After this patch, new
entries on changelogs - including existing changelogs - will be stored
as the fulltext of that data (likely compressed). No delta computation
will be performed.

An overview of delta chains and data justifying this change follows.

Revlogs try to store entries as a delta against a previous entry (either
a parent revision in the case of generaldelta or the previous physical
revision when not using generaldelta). Most of the time this is the
correct thing to do: it frequently results in less CPU usage and smaller
storage.

Delta chains are most effective when the base revision being deltad
against is similar to the current data. This tends to occur naturally
for manifests and file data, since only small parts of each tend to
change with each revision. Changelogs, however, are a different story.

Changelog entries represent changesets/commits. And unless commits in a
repository are homogonous (same author, changing same files, similar
commit messages, etc), a delta from one entry to the next tends to be
relatively large compared to the size of the entry. This means that
delta chains tend to be short. How short? Here is the full vs delta
revision breakdown on some real world repos:

Repo             % Full    % Delta   Max Length
hg                45.8       54.2        6
mozilla-central   42.4       57.6        8
mozilla-unified   42.5       57.5       17
pypy              46.1       53.9        6
python-zstandard  46.1       53.9        3

(I threw in python-zstandard as an example of a repo that is homogonous.
It contains a small Python project with changes all from the same
author.)

Contrast this with the manifest revlog for these repos, where 99+% of
revisions are deltas and delta chains run into the thousands.

So delta chains aren't as useful on changelogs. But even a short delta
chain may provide benefits. Let's measure that.

Delta chains may require less CPU to read revisions if the CPU time
spent reading smaller deltas is less than the CPU time used to
decompress larger individual entries. We can measure this via
`hg perfrevlog -c -d 1` to iterate a revlog to resolve each revision's
fulltext. Here are the results of that command on a repo using delta
chains in its changelog and on a repo without delta chains:

hg (forward)
! wall 0.407008 comb 0.410000 user 0.410000 sys 0.000000 (best of 25)
! wall 0.390061 comb 0.390000 user 0.390000 sys 0.000000 (best of 26)

hg (reverse)
! wall 0.515221 comb 0.520000 user 0.520000 sys 0.000000 (best of 19)
! wall 0.400018 comb 0.400000 user 0.390000 sys 0.010000 (best of 25)

mozilla-central (forward)
! wall 4.508296 comb 4.490000 user 4.490000 sys 0.000000 (best of 3)
! wall 4.370222 comb 4.370000 user 4.350000 sys 0.020000 (best of 3)

mozilla-central (reverse)
! wall 5.758995 comb 5.760000 user 5.720000 sys 0.040000 (best of 3)
! wall 4.346503 comb 4.340000 user 4.320000 sys 0.020000 (best of 3)

mozilla-unified (forward)
! wall 4.957088 comb 4.950000 user 4.940000 sys 0.010000 (best of 3)
! wall 4.660528 comb 4.650000 user 4.630000 sys 0.020000 (best of 3)

mozilla-unified (reverse)
! wall 6.119827 comb 6.110000 user 6.090000 sys 0.020000 (best of 3)
! wall 4.675136 comb 4.670000 user 4.670000 sys 0.000000 (best of 3)

pypy (forward)
! wall 1.231122 comb 1.240000 user 1.230000 sys 0.010000 (best of 8)
! wall 1.164896 comb 1.160000 user 1.160000 sys 0.000000 (best of 9)

pypy (reverse)
! wall 1.467049 comb 1.460000 user 1.460000 sys 0.000000 (best of 7)
! wall 1.160200 comb 1.170000 user 1.160000 sys 0.010000 (best of 9)

The data clearly shows that it takes less wall and CPU time to resolve
revisions when there are no delta chains in the changelogs, regardless
of the direction of traversal. Furthermore, not using a delta chain
means that fulltext resolution in reverse is as fast as iterating
forward. So not using delta chains on the changelog is a clear CPU win
for reading operations.

An example of a user-visible operation showing this speed-up is revset
evaluation. Here are results for
`hg perfrevset 'author(gps) or author(mpm)'`:

hg
! wall 1.655506 comb 1.660000 user 1.650000 sys 0.010000 (best of 6)
! wall 1.612723 comb 1.610000 user 1.600000 sys 0.010000 (best of 7)

mozilla-central
! wall 17.629826 comb 17.640000 user 17.600000 sys 0.040000 (best of 3)
! wall 17.311033 comb 17.300000 user 17.260000 sys 0.040000 (best of 3)

What about 00changelog.i size?

Repo                Delta Chains     No Delta Chains
hg                    7,033,250         6,976,771
mozilla-central      82,978,748        81,574,623
mozilla-unified      88,112,349        86,702,162
pypy                 20,740,699        20,659,741

The data shows that removing delta chains from the changelog makes the
changelog smaller.

Delta chains are also used during changegroup generation. This
operation essentially converts a series of revisions to one large
delta chain. And changegroup generation is smart: if the delta in
the revlog matches what the changegroup is emitting, it will reuse
the delta instead of recalculating it. We can measure the impact
removing changelog delta chains has on changegroup generation via
`hg perfchangegroupchangelog`:

hg
! wall 1.589245 comb 1.590000 user 1.590000 sys 0.000000 (best of 7)
! wall 1.788060 comb 1.790000 user 1.790000 sys 0.000000 (best of 6)

mozilla-central
! wall 17.382585 comb 17.380000 user 17.340000 sys 0.040000 (best of 3)
! wall 20.161357 comb 20.160000 user 20.120000 sys 0.040000 (best of 3)

mozilla-unified
! wall 18.722839 comb 18.720000 user 18.680000 sys 0.040000 (best of 3)
! wall 21.168075 comb 21.170000 user 21.130000 sys 0.040000 (best of 3)

pypy
! wall 4.828317 comb 4.830000 user 4.820000 sys 0.010000 (best of 3)
! wall 5.415455 comb 5.420000 user 5.410000 sys 0.010000 (best of 3)

The data shows eliminating delta chains makes the changelog part of
changegroup generation slower. This is expected since we now have to
compute deltas for revisions where we could recycle the delta before.

It is worth putting this regression into context of overall changegroup
times. Here is the rough total CPU time spent in changegroup generation
for various repos while using delta chains on the changelog:

Repo              CPU Time (s)    CPU Time w/ compression
hg                  4.50              7.05
mozilla-central   111.1             222.0
pypy               28.68             75.5

Before compression, removing delta chains from the changegroup adds
~4.4% overhead to hg changegroup generation, 1.3% to mozilla-central,
and 2.0% to pypy. When you factor in zlib compression, these percentages
are roughly divided by 2.

While the increased CPU usage for changegroup generation is unfortunate,
I think it is acceptable because the percentage is small, server
operators (those likely impacted most by this) have other mechanisms
to mitigate CPU consumption (namely reducing zlib compression level and
pre-generated clone bundles), and because there is room to optimize this
in the future. For example, we could use the nullid as the base revision,
effectively encoding the full revision for each entry in the changegroup.
When doing this, `hg perfchangegroupchangelog` nearly halves:

mozilla-unified
! wall 21.168075 comb 21.170000 user 21.130000 sys 0.040000 (best of 3)
! wall 11.196461 comb 11.200000 user 11.190000 sys 0.010000 (best of 3)

This looks very promising as a future optimization opportunity.

It's worth that the changes in test-acl.t to the changegroup part size.
This is because revision 6 in the changegroup had a delta chain of
length 2 before and after this patch the base revision is nullrev.
When the base revision is nullrev, cg2packer.deltaparent() hardcodes
the *previous* revision from the changegroup as the delta parent.
This caused the delta in the changegroup to switch base revisions,
the delta to change, and the size to change accordingly. While the
size increased in this case, I think sizes will remain the same
on average, as the delta base for changelog revisions doesn't matter
too much (as this patch shows). So, I don't consider this a regression.

Test that qpush cleans things up if it doesn't complete

  $ echo "[extensions]" >> $HGRCPATH
  $ echo "mq=" >> $HGRCPATH
  $ hg init repo
  $ cd repo
  $ echo foo > foo
  $ hg ci -Am 'add foo'
  adding foo
  $ touch untracked-file
  $ echo 'syntax: glob' > .hgignore
  $ echo '.hgignore' >> .hgignore
  $ hg qinit

test qpush on empty series

  $ hg qpush
  no patches in series
  $ hg qnew patch1
  $ echo >> foo
  $ hg qrefresh -m 'patch 1'
  $ hg qnew patch2
  $ echo bar > bar
  $ hg add bar
  $ hg qrefresh -m 'patch 2'
  $ hg qnew --config 'mq.plain=true' -U bad-patch
  $ echo >> foo
  $ hg qrefresh
  $ hg qpop -a
  popping bad-patch
  popping patch2
  popping patch1
  patch queue now empty
  $ $PYTHON -c 'print "\xe9"' > message
  $ cat .hg/patches/bad-patch >> message
  $ mv message .hg/patches/bad-patch
  $ cat > $TESTTMP/wrapplayback.py <<EOF
  > import os
  > from mercurial import extensions, transaction
  > def wrapplayback(orig,
  >                  journal, report, opener, vfsmap, entries, backupentries,
  >                  unlink=True):
  >     orig(journal, report, opener, vfsmap, entries, backupentries, unlink)
  >     # Touching files truncated at "transaction.abort" causes
  >     # forcible re-loading invalidated filecache properties
  >     # (including repo.changelog)
  >     for f, o, _ignore in entries:
  >         if o or not unlink:
  >             os.utime(opener.join(f), (0.0, 0.0))
  > def extsetup(ui):
  >     extensions.wrapfunction(transaction, '_playback', wrapplayback)
  > EOF
  $ hg qpush -a --config extensions.wrapplayback=$TESTTMP/wrapplayback.py  && echo 'qpush succeeded?!'
  applying patch1
  applying patch2
  applying bad-patch
  transaction abort!
  rollback completed
  cleaning up working directory...
  reverting foo
  done
  abort: decoding near '\xe9': 'ascii' codec can't decode byte 0xe9 in position 0: ordinal not in range(128)! (esc)
  [255]
  $ hg parents
  changeset:   0:bbd179dfa0a7
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     add foo
  

test corrupt status file
  $ hg qpush
  applying patch1
  now at: patch1
  $ cp .hg/patches/status .hg/patches/status.orig
  $ hg qpop
  popping patch1
  patch queue now empty
  $ cp .hg/patches/status.orig .hg/patches/status
  $ hg qpush
  abort: working directory revision is not qtip
  [255]
  $ rm .hg/patches/status .hg/patches/status.orig


bar should be gone; other unknown/ignored files should still be around

  $ hg status -A
  ? untracked-file
  I .hgignore
  C foo

preparing qpush of a missing patch

  $ hg qpop -a
  no patches applied
  $ hg qpush
  applying patch1
  now at: patch1
  $ rm .hg/patches/patch2

now we expect the push to fail, but it should NOT complain about patch1

  $ hg qpush
  applying patch2
  unable to read patch2
  now at: patch1
  [1]

preparing qpush of missing patch with no patch applied

  $ hg qpop -a
  popping patch1
  patch queue now empty
  $ rm .hg/patches/patch1

qpush should fail the same way as below

  $ hg qpush
  applying patch1
  unable to read patch1
  [1]

Test qpush to a patch below the currently applied patch.

  $ hg qq -c guardedseriesorder
  $ hg qnew a
  $ hg qguard +block
  $ hg qnew b
  $ hg qnew c

  $ hg qpop -a
  popping c
  popping b
  popping a
  patch queue now empty

try to push and pop while a is guarded

  $ hg qpush a
  cannot push 'a' - guarded by '+block'
  [1]
  $ hg qpush -a
  applying b
  patch b is empty
  applying c
  patch c is empty
  now at: c

now try it when a is unguarded, and we're at the top of the queue

  $ hg qapplied -v
  0 G a
  1 A b
  2 A c
  $ hg qsel block
  $ hg qpush b
  abort: cannot push to a previous patch: b
  [255]
  $ hg qpush a
  abort: cannot push to a previous patch: a
  [255]

and now we try it one more time with a unguarded, while we're not at the top of the queue

  $ hg qpop b
  popping c
  now at: b
  $ hg qpush a
  abort: cannot push to a previous patch: a
  [255]

test qpop --force and backup files

  $ hg qpop -a
  popping b
  patch queue now empty
  $ hg qq --create force
  $ echo a > a
  $ echo b > b
  $ echo c > c
  $ hg ci -Am add a b c
  $ echo a >> a
  $ hg rm b
  $ hg rm c
  $ hg qnew p1
  $ echo a >> a
  $ echo bb > b
  $ hg add b
  $ echo cc > c
  $ hg add c
  $ hg qpop --force --verbose
  saving current version of a as a.orig
  saving current version of b as b.orig
  saving current version of c as c.orig
  popping p1
  patch queue now empty
  $ hg st
  ? a.orig
  ? b.orig
  ? c.orig
  ? untracked-file
  $ cat a.orig
  a
  a
  a
  $ cat b.orig
  bb
  $ cat c.orig
  cc

test qpop --force --no-backup

  $ hg qpush
  applying p1
  now at: p1
  $ rm a.orig
  $ echo a >> a
  $ hg qpop --force --no-backup --verbose
  popping p1
  patch queue now empty
  $ test -f a.orig && echo 'error: backup with --no-backup'
  [1]

test qpop --keep-changes

  $ hg qpush
  applying p1
  now at: p1
  $ hg qpop --keep-changes --force
  abort: cannot use both --force and --keep-changes
  [255]
  $ echo a >> a
  $ hg qpop --keep-changes
  abort: local changes found, qrefresh first
  [255]
  $ hg revert -qa a
  $ rm a
  $ hg qpop --keep-changes
  abort: local changes found, qrefresh first
  [255]
  $ hg rm -A a
  $ hg qpop --keep-changes
  abort: local changes found, qrefresh first
  [255]
  $ hg revert -qa a
  $ echo b > b
  $ hg add b
  $ hg qpop --keep-changes
  abort: local changes found, qrefresh first
  [255]
  $ hg forget b
  $ echo d > d
  $ hg add d
  $ hg qpop --keep-changes
  popping p1
  patch queue now empty
  $ hg forget d
  $ rm d

test qpush --force and backup files

  $ echo a >> a
  $ hg qnew p2
  $ echo b >> b
  $ echo d > d
  $ echo e > e
  $ hg add d e
  $ hg rm c
  $ hg qnew p3
  $ hg qpop -a
  popping p3
  popping p2
  patch queue now empty
  $ echo a >> a
  $ echo b1 >> b
  $ echo d1 > d
  $ hg add d
  $ echo e1 > e
  $ hg qpush -a --force --verbose
  applying p2
  saving current version of a as a.orig
  patching file a
  committing files:
  a
  committing manifest
  committing changelog
  applying p3
  saving current version of b as b.orig
  saving current version of d as d.orig
  patching file b
  patching file c
  patching file d
  file d already exists
  1 out of 1 hunks FAILED -- saving rejects to file d.rej
  patching file e
  file e already exists
  1 out of 1 hunks FAILED -- saving rejects to file e.rej
  patch failed to apply
  committing files:
  b
  committing manifest
  committing changelog
  patch failed, rejects left in working directory
  errors during apply, please fix and qrefresh p3
  [2]
  $ cat a.orig
  a
  a
  $ cat b.orig
  b
  b1
  $ cat d.orig
  d1

test qpush --force --no-backup

  $ hg revert -qa
  $ hg qpop -a
  popping p3
  popping p2
  patch queue now empty
  $ echo a >> a
  $ rm a.orig
  $ hg qpush --force --no-backup --verbose
  applying p2
  patching file a
  committing files:
  a
  committing manifest
  committing changelog
  now at: p2
  $ test -f a.orig && echo 'error: backup with --no-backup'
  [1]

test qgoto --force --no-backup

  $ hg qpop
  popping p2
  patch queue now empty
  $ echo a >> a
  $ hg qgoto --force --no-backup p2 --verbose
  applying p2
  patching file a
  committing files:
  a
  committing manifest
  committing changelog
  now at: p2
  $ test -f a.orig && echo 'error: backup with --no-backup'
  [1]

test qpush --keep-changes

  $ hg qpush --keep-changes --force
  abort: cannot use both --force and --keep-changes
  [255]
  $ hg qpush --keep-changes --exact
  abort: cannot use --exact and --keep-changes together
  [255]
  $ echo b >> b
  $ hg qpush --keep-changes
  applying p3
  abort: conflicting local changes found
  (did you forget to qrefresh?)
  [255]
  $ rm b
  $ hg qpush --keep-changes
  applying p3
  abort: conflicting local changes found
  (did you forget to qrefresh?)
  [255]
  $ hg rm -A b
  $ hg qpush --keep-changes
  applying p3
  abort: conflicting local changes found
  (did you forget to qrefresh?)
  [255]
  $ hg revert -aq b
  $ echo d > d
  $ hg add d
  $ hg qpush --keep-changes
  applying p3
  abort: conflicting local changes found
  (did you forget to qrefresh?)
  [255]
  $ hg forget d
  $ rm d
  $ hg qpop
  popping p2
  patch queue now empty
  $ echo b >> b
  $ hg qpush -a --keep-changes
  applying p2
  applying p3
  abort: conflicting local changes found
  (did you forget to qrefresh?)
  [255]
  $ hg qtop
  p2
  $ hg parents --template "{rev} {desc}\n"
  2 imported patch p2
  $ hg st b
  M b
  $ cat b
  b
  b

test qgoto --keep-changes

  $ hg revert -aq b
  $ rm e
  $ hg qgoto --keep-changes --force p3
  abort: cannot use both --force and --keep-changes
  [255]
  $ echo a >> a
  $ hg qgoto --keep-changes p3
  applying p3
  now at: p3
  $ hg st a
  M a
  $ hg qgoto --keep-changes p2
  popping p3
  now at: p2
  $ hg st a
  M a

test mq.keepchanges setting

  $ hg --config mq.keepchanges=1 qpush
  applying p3
  now at: p3
  $ hg st a
  M a
  $ hg --config mq.keepchanges=1 qpop
  popping p3
  now at: p2
  $ hg st a
  M a
  $ hg --config mq.keepchanges=1 qgoto p3
  applying p3
  now at: p3
  $ hg st a
  M a
  $ echo b >> b
  $ hg --config mq.keepchanges=1 qpop --force --config 'ui.origbackuppath=.hg/origbackups'
  popping p3
  now at: p2
  $ hg st b
  $ hg --config mq.keepchanges=1 qpush --exact
  abort: local changes found, qrefresh first
  [255]
  $ hg revert -qa a
  $ hg qpop
  popping p2
  patch queue now empty
  $ echo a >> a
  $ hg --config mq.keepchanges=1 qpush --force
  applying p2
  now at: p2
  $ hg st a

test previous qpop (with --force and --config) saved .orig files to where user
wants them
  $ ls .hg/origbackups
  b.orig
  $ rm -rf .hg/origbackups

  $ cd ..