view tests/test-absorb.t @ 51681:522b4d729e89

mmap: populate the mapping by default

Without pre-population, accessing all data through a mmap can result in many
pagefault, reducing performance significantly. If the mmap is prepopulated, the
performance can no longer get slower than a full read.
(See benchmark number below)

In some cases were very few data is read, prepopulating can be overkill and
slower than populating on access (through page fault). So that behavior can be
controlled when the caller can pre-determine the best behavior.
(See benchmark number below)

In addition, testing with populating in a secondary thread yield great result
combining the best of each approach. This might be implemented in later
changesets.

In all cases, using mmap has a great effect on memory usage when many processes
run in parallel on the same machine.

### Benchmarks

# What did I run

A couple of month back I ran a large benchmark campaign to assess the impact of
various approach for using mmap with the revlog (and other files), it
highlighted a few benchmarks that capture the impact of the changes well. So to
validate this change I checked the following:

- log command displaying various revisions
  (read the changelog index)
- log command displaying the patch of listed revisions
  (read the changelog index, the manifest index and a few files indexes)
- unbundling a few revisions
  (read and write changelog, manifest and few files indexes, and walk the graph
  to update some cache)
- pushing a few revisions
  (read and write changelog, manifest and few files indexes, walk the graph to
  update some cache, performs various accesses locally and remotely during
  discovery)

Benchmarks were run using the default module policy (c+py) and the rust one. No
significant difference were found between the two implementation, so we will
present result using the default policy (unless otherwise specified).

I ran them on a few repositories :

- mercurial: a "public changeset only" copy of mercurial from 2018-08-01 using
  zstd compression and sparse-revlog

- pypy: a copy of pypy from 2018-08-01 using zstd compression and sparse-revlog

- netbeans: a copy of netbeans from 2018-08-01 using zstd compression and
  sparse-revlog

- mozilla-try: a copy of mozilla-try from 2019-02-18 using zstd compression and
  sparse-revlog

- mozilla-try persistent-nodemap: Same as the above but with a persistent
  nodemap. Used for the log --patch benchmark only

# Results

For the smaller repositories (mercurial, pypy), the impact of mmap is almost
imperceptible, other cost dominating the operation. The impact of prepopulating
is undiscernible in the benchmark we ran.

For larger repositories the benchmark support explanation given above:

On netbeans, the log can be about 1% faster without repopulation (for a
difference < 100ms) but unbundle becomes a bit slower, even when small.

### data-env-vars.name                             = netbeans-2018-08-01-zstd-sparse-revlog
  # benchmark.name                                 = hg.command.unbundle
  # benchmark.variants.issue6528                   = disabled
  # benchmark.variants.reuse-external-delta-parent = yes
  # benchmark.variants.revs                        = any-1-extra-rev
  # benchmark.variants.source                      = unbundle
  # benchmark.variants.verbosity                   = quiet
with-populate: 0.240157
no-populate:   0.265087  (+10.38%, +0.02)
  # benchmark.variants.revs                        = any-100-extra-rev
with-populate: 1.459518
no-populate:   1.481290   (+1.49%, +0.02)
 ## benchmark.name                                 = hg.command.push
  # benchmark.variants.explicit-rev                = none
  # benchmark.variants.issue6528                   = disabled
  # benchmark.variants.protocol                    = ssh
  # benchmark.variants.reuse-external-delta-parent = yes
  # benchmark.variants.revs                        = any-1-extra-rev
with-populate: 0.771919
no-populate:   0.792025   (+2.60%, +0.02)
  # benchmark.variants.revs                        = any-100-extra-rev
with-populate: 1.459518
no-populate:   1.481290   (+1.49%, +0.02)


For mozilla-try, the "slow down" from pre-populate for small `hg log` is more
visible, but still small in absolute time. (using rust value for the persistent
nodemap value to be relevant).

### data-env-vars.name            = mozilla-try-2019-02-18-ds2-pnm
  # benchmark.name                = hg.command.log
  # bin-env-vars.hg.flavor        = rust
  # benchmark.variants.patch      = yes
  # benchmark.variants.limit-rev  = 1
with-populate: 0.237813
no-populate:   0.229452   (-3.52%, -0.01)
  # benchmark.variants.limit-rev  = 10
  # benchmark.variants.patch      = yes
with-populate: 1.213578
no-populate:   1.205189
### data-env-vars.name            = mozilla-try-2019-02-18-zstd-sparse-revlog
  # benchmark.variants.limit-rev  = 1000
  # benchmark.variants.patch      = no
  # benchmark.variants.rev        = tip
with-populate: 0.198607
no-populate:   0.195038   (-1.80%, -0.00)

However pre-populating provide a significant boost on more complex operations
like unbundle or push:

### data-env-vars.name                             = mozilla-try-2019-02-18-zstd-sparse-revlog
  # benchmark.name                                 = hg.command.push
  # benchmark.variants.explicit-rev                = none
  # benchmark.variants.issue6528                   = disabled
  # benchmark.variants.protocol                    = ssh
  # benchmark.variants.reuse-external-delta-parent = yes
  # benchmark.variants.revs                        = any-1-extra-rev
with-populate: 4.798632
no-populate:   4.953295   (+3.22%, +0.15)
  # benchmark.variants.revs                        = any-100-extra-rev
with-populate: 4.903618
no-populate:   5.014963   (+2.27%, +0.11)
 ## benchmark.name                                 = hg.command.unbundle
  # benchmark.variants.revs                        = any-1-extra-rev
with-populate: 1.423411
no-populate:   1.585365  (+11.38%, +0.16)
  # benchmark.variants.revs                        = any-100-extra-rev
with-populate: 1.537909
no-populate:   1.688489   (+9.79%, +0.15)

  $ cat >> $HGRCPATH << EOF
  > [extensions]
  > absorb=
  > EOF

  $ sedi() { # workaround check-code
  > pattern="$1"
  > shift
  > for i in "$@"; do
  >     sed "$pattern" "$i" > "$i".tmp
  >     mv "$i".tmp "$i"
  > done
  > }

  $ hg init repo1
  $ cd repo1

Do not crash with empty repo:

  $ hg absorb
  abort: no mutable changeset to change
  [10]

Make some commits:

  $ for i in 1 2 3 4 5; do
  >   echo $i >> a
  >   hg commit -A a -m "commit $i" -q
  > done

  $ hg annotate a
  0: 1
  1: 2
  2: 3
  3: 4
  4: 5

Change a few lines:

  $ cat > a <<EOF
  > 1a
  > 2b
  > 3
  > 4d
  > 5e
  > EOF

Preview absorb changes:

  $ hg absorb --print-changes --dry-run
  showing changes for a
          @@ -0,2 +0,2 @@
  4ec16f8 -1
  5c5f952 -2
  4ec16f8 +1a
  5c5f952 +2b
          @@ -3,2 +3,2 @@
  ad8b8b7 -4
  4f55fa6 -5
  ad8b8b7 +4d
  4f55fa6 +5e
  
  4 changesets affected
  4f55fa6 commit 5
  ad8b8b7 commit 4
  5c5f952 commit 2
  4ec16f8 commit 1

Run absorb:

  $ hg absorb --apply-changes
  saved backup bundle to * (glob)
  2 of 2 chunk(s) applied
  $ hg annotate a
  0: 1a
  1: 2b
  2: 3
  3: 4d
  4: 5e

Delete a few lines and related commits will be removed if they will be empty:

  $ cat > a <<EOF
  > 2b
  > 4d
  > EOF
  $ echo y | hg absorb --config ui.interactive=1
  showing changes for a
          @@ -0,1 +0,0 @@
  f548282 -1a
          @@ -2,1 +1,0 @@
  ff5d556 -3
          @@ -4,1 +2,0 @@
  84e5416 -5e
  
  3 changesets affected
  84e5416 commit 5
  ff5d556 commit 3
  f548282 commit 1
  apply changes (y/N)?  y
  saved backup bundle to * (glob)
  3 of 3 chunk(s) applied
  $ hg annotate a
  1: 2b
  2: 4d
  $ hg log -T '{rev} {desc}\n' -Gp
  @  2 commit 4
  |  diff -r 1cae118c7ed8 -r 58a62bade1c6 a
  |  --- a/a	Thu Jan 01 00:00:00 1970 +0000
  |  +++ b/a	Thu Jan 01 00:00:00 1970 +0000
  |  @@ -1,1 +1,2 @@
  |   2b
  |  +4d
  |
  o  1 commit 2
  |  diff -r 84add69aeac0 -r 1cae118c7ed8 a
  |  --- a/a	Thu Jan 01 00:00:00 1970 +0000
  |  +++ b/a	Thu Jan 01 00:00:00 1970 +0000
  |  @@ -0,0 +1,1 @@
  |  +2b
  |
  o  0 commit 1
  

Non 1:1 map changes will be ignored:

  $ echo 1 > a
  $ hg absorb --apply-changes
  nothing applied
  [1]

The prompt is not given if there are no changes to be applied, even if there
are some changes that won't be applied:

  $ hg absorb
  showing changes for a
          @@ -0,2 +0,1 @@
          -2b
          -4d
          +1
  
  0 changesets affected
  nothing applied
  [1]

Insertaions:

  $ cat > a << EOF
  > insert before 2b
  > 2b
  > 4d
  > insert aftert 4d
  > EOF
  $ hg absorb -q --apply-changes
  $ hg status
  $ hg annotate a
  1: insert before 2b
  1: 2b
  2: 4d
  2: insert aftert 4d

Bookmarks are moved:

  $ hg bookmark -r 1 b1
  $ hg bookmark -r 2 b2
  $ hg bookmark ba
  $ hg bookmarks
     b1                        1:b35060a57a50
     b2                        2:946e4bc87915
   * ba                        2:946e4bc87915
  $ sedi 's/insert/INSERT/' a
  $ hg absorb -q --apply-changes
  $ hg status
  $ hg bookmarks
     b1                        1:a4183e9b3d31
     b2                        2:c9b20c925790
   * ba                        2:c9b20c925790

Non-modified files are ignored:

  $ touch b
  $ hg commit -A b -m b
  $ touch c
  $ hg add c
  $ hg rm b
  $ hg absorb --apply-changes
  nothing applied
  [1]
  $ sedi 's/INSERT/Insert/' a
  $ hg absorb --apply-changes
  saved backup bundle to * (glob)
  2 of 2 chunk(s) applied
  $ hg status
  A c
  R b

Public commits will not be changed:

  $ hg phase -p 1
  $ sedi 's/Insert/insert/' a
  $ hg absorb -pn
  showing changes for a
          @@ -0,1 +0,1 @@
          -Insert before 2b
          +insert before 2b
          @@ -3,1 +3,1 @@
  85b4e0e -Insert aftert 4d
  85b4e0e +insert aftert 4d
  
  1 changesets affected
  85b4e0e commit 4
  $ hg absorb --apply-changes
  saved backup bundle to * (glob)
  1 of 2 chunk(s) applied
  $ hg diff -U 0
  diff -r 1c8eadede62a a
  --- a/a	Thu Jan 01 00:00:00 1970 +0000
  +++ b/a	* (glob)
  @@ -1,1 +1,1 @@
  -Insert before 2b
  +insert before 2b
  $ hg annotate a
  1: Insert before 2b
  1: 2b
  2: 4d
  2: insert aftert 4d

  $ hg co -qC 1
  $ sedi 's/Insert/insert/' a
  $ hg absorb --apply-changes
  abort: no mutable changeset to change
  [10]

Make working copy clean:

  $ hg co -qC ba
  $ rm c
  $ hg status

Merge commit will not be changed:

  $ echo 1 > m1
  $ hg commit -A m1 -m m1
  $ hg bookmark -q -i m1
  $ hg update -q '.^'
  $ echo 2 > m2
  $ hg commit -q -A m2 -m m2
  $ hg merge -q m1
  $ hg commit -m merge
  $ hg bookmark -d m1
  $ hg log -G -T '{rev} {desc} {phase}\n'
  @    6 merge draft
  |\
  | o  5 m2 draft
  | |
  o |  4 m1 draft
  |/
  o  3 b draft
  |
  o  2 commit 4 draft
  |
  o  1 commit 2 public
  |
  o  0 commit 1 public
  
  $ echo 2 >> m1
  $ echo 2 >> m2
  $ hg absorb --apply-changes
  abort: cannot absorb into a merge
  [10]
  $ hg revert -q -C m1 m2

Use a new repo:

  $ cd ..
  $ hg init repo2
  $ cd repo2

Make some commits to multiple files:

  $ for f in a b; do
  >   for i in 1 2; do
  >     echo $f line $i >> $f
  >     hg commit -A $f -m "commit $f $i" -q
  >   done
  > done

Use pattern to select files to be fixed up:

  $ sedi 's/line/Line/' a b
  $ hg status
  M a
  M b
  $ hg absorb --apply-changes a
  saved backup bundle to * (glob)
  1 of 1 chunk(s) applied
  $ hg status
  M b
  $ hg absorb --apply-changes --exclude b
  nothing applied
  [1]
  $ hg absorb --apply-changes b
  saved backup bundle to * (glob)
  1 of 1 chunk(s) applied
  $ hg status
  $ cat a b
  a Line 1
  a Line 2
  b Line 1
  b Line 2

Test config option absorb.max-stack-size:

  $ sedi 's/Line/line/' a b
  $ hg log -T '{rev}:{node} {desc}\n'
  3:712d16a8f445834e36145408eabc1d29df05ec09 commit b 2
  2:74cfa6294160149d60adbf7582b99ce37a4597ec commit b 1
  1:28f10dcf96158f84985358a2e5d5b3505ca69c22 commit a 2
  0:f9a81da8dc53380ed91902e5b82c1b36255a4bd0 commit a 1
  $ hg --config absorb.max-stack-size=1 absorb -pn
  absorb: only the recent 1 changesets will be analysed
  showing changes for a
          @@ -0,2 +0,2 @@
          -a Line 1
          -a Line 2
          +a line 1
          +a line 2
  showing changes for b
          @@ -0,2 +0,2 @@
          -b Line 1
  712d16a -b Line 2
          +b line 1
  712d16a +b line 2
  
  1 changesets affected
  712d16a commit b 2

Test obsolete markers creation:

  $ cat >> $HGRCPATH << EOF
  > [experimental]
  > evolution=createmarkers
  > [absorb]
  > add-noise=1
  > EOF

  $ hg --config absorb.max-stack-size=3 absorb -a
  absorb: only the recent 3 changesets will be analysed
  2 of 2 chunk(s) applied
  $ hg log -T '{rev}:{node|short} {desc} {get(extras, "absorb_source")}\n'
  6:3dfde4199b46 commit b 2 712d16a8f445834e36145408eabc1d29df05ec09
  5:99cfab7da5ff commit b 1 74cfa6294160149d60adbf7582b99ce37a4597ec
  4:fec2b3bd9e08 commit a 2 28f10dcf96158f84985358a2e5d5b3505ca69c22
  0:f9a81da8dc53 commit a 1 
  $ hg absorb --apply-changes
  1 of 1 chunk(s) applied
  $ hg log -T '{rev}:{node|short} {desc} {get(extras, "absorb_source")}\n'
  10:e1c8c1e030a4 commit b 2 3dfde4199b4610ea6e3c6fa9f5bdad8939d69524
  9:816c30955758 commit b 1 99cfab7da5ffdaf3b9fc6643b14333e194d87f46
  8:5867d584106b commit a 2 fec2b3bd9e0834b7cb6a564348a0058171aed811
  7:8c76602baf10 commit a 1 f9a81da8dc53380ed91902e5b82c1b36255a4bd0

Executable files:

  $ cat >> $HGRCPATH << EOF
  > [diff]
  > git=True
  > EOF
  $ cd ..
  $ hg init repo3
  $ cd repo3

#if execbit
  $ echo > foo.py
  $ chmod +x foo.py
  $ hg add foo.py
  $ hg commit -mfoo
#else
  $ hg import -q --bypass - <<EOF
  > # HG changeset patch
  > foo
  > 
  > diff --git a/foo.py b/foo.py
  > new file mode 100755
  > --- /dev/null
  > +++ b/foo.py
  > @@ -0,0 +1,1 @@
  > +
  > EOF
  $ hg up -q
#endif

  $ echo bla > foo.py
  $ hg absorb --dry-run --print-changes
  showing changes for foo.py
          @@ -0,1 +0,1 @@
  99b4ae7 -
  99b4ae7 +bla
  
  1 changesets affected
  99b4ae7 foo
  $ hg absorb --dry-run --interactive --print-changes
  diff -r 99b4ae712f84 foo.py
  1 hunks, 1 lines changed
  examine changes to 'foo.py'?
  (enter ? for help) [Ynesfdaq?] y
  
  @@ -1,1 +1,1 @@
  -
  +bla
  record this change to 'foo.py'?
  (enter ? for help) [Ynesfdaq?] y
  
  showing changes for foo.py
          @@ -0,1 +0,1 @@
  99b4ae7 -
  99b4ae7 +bla
  
  1 changesets affected
  99b4ae7 foo
  $ hg absorb --apply-changes
  1 of 1 chunk(s) applied
  $ hg diff -c .
  diff --git a/foo.py b/foo.py
  new file mode 100755
  --- /dev/null
  +++ b/foo.py
  @@ -0,0 +1,1 @@
  +bla
  $ hg diff

Remove lines may delete changesets:

  $ cd ..
  $ hg init repo4
  $ cd repo4
  $ cat > a <<EOF
  > 1
  > 2
  > EOF
  $ hg commit -m a12 -A a
  $ cat > b <<EOF
  > 1
  > 2
  > EOF
  $ hg commit -m b12 -A b
  $ echo 3 >> b
  $ hg commit -m b3
  $ echo 4 >> b
  $ hg commit -m b4
  $ echo 1 > b
  $ echo 3 >> a
  $ hg absorb -pn
  showing changes for a
          @@ -2,0 +2,1 @@
  bfafb49 +3
  showing changes for b
          @@ -1,3 +1,0 @@
  1154859 -2
  30970db -3
  a393a58 -4
  
  4 changesets affected
  a393a58 b4
  30970db b3
  1154859 b12
  bfafb49 a12
  $ hg absorb -av | grep became
  0:bfafb49242db: 1 file(s) changed, became 4:1a2de97fc652
  1:115485984805: 2 file(s) changed, became 5:0c930dfab74c
  2:30970dbf7b40: became empty and was dropped
  3:a393a58b9a85: became empty and was dropped
  $ hg log -T '{rev} {desc}\n' -Gp
  @  5 b12
  |  diff --git a/b b/b
  |  new file mode 100644
  |  --- /dev/null
  |  +++ b/b
  |  @@ -0,0 +1,1 @@
  |  +1
  |
  o  4 a12
     diff --git a/a b/a
     new file mode 100644
     --- /dev/null
     +++ b/a
     @@ -0,0 +1,3 @@
     +1
     +2
     +3
  

Setting config rewrite.empty-successor=keep causes empty changesets to get committed:

  $ cd ..
  $ hg init repo4a
  $ cd repo4a
  $ cat > a <<EOF
  > 1
  > 2
  > EOF
  $ hg commit -m a12 -A a
  $ cat > b <<EOF
  > 1
  > 2
  > EOF
  $ hg commit -m b12 -A b
  $ echo 3 >> b
  $ hg commit -m b3
  $ echo 4 >> b
  $ hg commit -m b4
  $ hg commit -m empty --config ui.allowemptycommit=True
  $ echo 1 > b
  $ echo 3 >> a
  $ hg absorb -pn
  showing changes for a
          @@ -2,0 +2,1 @@
  bfafb49 +3
  showing changes for b
          @@ -1,3 +1,0 @@
  1154859 -2
  30970db -3
  a393a58 -4
  
  4 changesets affected
  a393a58 b4
  30970db b3
  1154859 b12
  bfafb49 a12
  $ hg absorb -av --config rewrite.empty-successor=keep | grep became
  0:bfafb49242db: 1 file(s) changed, became 5:1a2de97fc652
  1:115485984805: 2 file(s) changed, became 6:0c930dfab74c
  2:30970dbf7b40: 2 file(s) changed, became empty as 7:df6574ae635c
  3:a393a58b9a85: 2 file(s) changed, became empty as 8:ad4bd3462c9e
  4:1bb0e8cff87a: 2 file(s) changed, became 9:2dbed75af996
  $ hg log -T '{rev} {desc}\n' -Gp
  @  9 empty
  |
  o  8 b4
  |
  o  7 b3
  |
  o  6 b12
  |  diff --git a/b b/b
  |  new file mode 100644
  |  --- /dev/null
  |  +++ b/b
  |  @@ -0,0 +1,1 @@
  |  +1
  |
  o  5 a12
     diff --git a/a b/a
     new file mode 100644
     --- /dev/null
     +++ b/a
     @@ -0,0 +1,3 @@
     +1
     +2
     +3
  

Use revert to make the current change and its parent disappear.
This should move us to the non-obsolete ancestor.

  $ cd ..
  $ hg init repo5
  $ cd repo5
  $ cat > a <<EOF
  > 1
  > 2
  > EOF
  $ hg commit -m a12 -A a
  $ hg id
  bfafb49242db tip
  $ echo 3 >> a
  $ hg commit -m a123 a
  $ echo 4 >> a
  $ hg commit -m a1234 a
  $ hg id
  82dbe7fd19f0 tip
  $ hg revert -r 0 a
  $ hg absorb -pn
  showing changes for a
          @@ -2,2 +2,0 @@
  f1c23dd -3
  82dbe7f -4
  
  2 changesets affected
  82dbe7f a1234
  f1c23dd a123
  $ hg absorb --apply-changes --verbose
  1:f1c23dd5d08d: became empty and was dropped
  2:82dbe7fd19f0: became empty and was dropped
  a: 1 of 1 chunk(s) applied
  $ hg id
  bfafb49242db tip

  $ cd ..
  $ hg init repo6
  $ cd repo6
  $ echo a1 > a
  $ touch b
  $ hg commit -m a -A a b
  $ hg branch foo -q
  $ echo b > b
  $ hg commit -m 'foo (child of 0cde1ae39321)'  # will become empty
  $ hg branch bar -q
  $ hg commit -m 'bar (child of e969dc86aefc)'  # is already empty
  $ echo a2 > a
  $ printf '' > b
  $ hg absorb --apply-changes --verbose | grep became
  0:0cde1ae39321: 1 file(s) changed, became 3:fc7fcdd90fdb
  1:e969dc86aefc: 2 file(s) changed, became 4:8fc6b2cb43a5
  2:0298954ced32: 2 file(s) changed, became 5:ca8386dc4e2c
  $ hg log -T '{rev}:{node|short} (branch: {branch}) {desc}\n' -G --stat
  @  5:ca8386dc4e2c (branch: bar) bar (child of 8fc6b2cb43a5)
  |
  o  4:8fc6b2cb43a5 (branch: foo) foo (child of fc7fcdd90fdb)
  |
  o  3:fc7fcdd90fdb (branch: default) a
      a |  1 +
      b |  0
      2 files changed, 1 insertions(+), 0 deletions(-)
  

  $ cd ..
  $ hg init repo7
  $ cd repo7
  $ echo a1 > a
  $ touch b
  $ hg commit -m a -A a b
  $ echo b > b
  $ hg commit -m foo --close-branch  # will become empty
  $ echo c > c
  $ hg commit -m reopen -A c -q
  $ hg commit -m bar --close-branch  # is already empty
  $ echo a2 > a
  $ printf '' > b
  $ hg absorb --apply-changes --verbose | grep became
  0:0cde1ae39321: 1 file(s) changed, became 4:fc7fcdd90fdb
  1:651b953d5764: 2 file(s) changed, became 5:0c9de988ecdc
  2:76017bba73f6: 2 file(s) changed, became 6:d53ac896eb25
  3:c7c1d67efc1d: 2 file(s) changed, became 7:66520267fe96
  $ hg up null -q  # to make visible closed heads
  $ hg log -T '{rev} {desc}\n' -G --stat
  _  7 bar
  |
  o  6 reopen
  |   c |  1 +
  |   1 files changed, 1 insertions(+), 0 deletions(-)
  |
  _  5 foo
  |
  o  4 a
      a |  1 +
      b |  0
      2 files changed, 1 insertions(+), 0 deletions(-)
  

  $ cd ..
  $ hg init repo8
  $ cd repo8
  $ echo a1 > a
  $ hg commit -m a -A a
  $ hg commit -m empty --config ui.allowemptycommit=True
  $ echo a2 > a
  $ hg absorb --apply-changes --verbose | grep became
  0:ecf99a8d6699: 1 file(s) changed, became 2:7e3ccf8e2fa5
  1:97f72456ae0d: 1 file(s) changed, became 3:2df488325d6f
  $ hg log -T '{rev} {desc}\n' -G --stat
  @  3 empty
  |
  o  2 a
      a |  1 +
      1 files changed, 1 insertions(+), 0 deletions(-)