tests/test-rebase-cache.t

revlog: use an LRU cache for delta chain bases

Profiling using statprof revealed a hotspot during changegroup
application calculating delta chain bases on generaldelta repos.
Essentially, revlog._addrevision() was performing a lot of redundant
work tracing the delta chain as part of determining when the chain
distance was acceptable. This was most pronounced when adding
revisions to manifests, which can have delta chains thousands of
revisions long.

There was a delta chain base cache on revlogs before, but it only
captured a single revision. This was acceptable before generaldelta,
when _addrevision would build deltas from the previous revision and
thus we'd pretty much guarantee a cache hit when resolving the delta
chain base on a subsequent _addrevision call. However, it isn't
suitable for generaldelta because parent revisions aren't necessarily
the last processed revision.

This patch converts the delta chain base cache to an LRU dict cache.
The cache can hold multiple entries, so generaldelta repos have a
higher chance of getting a cache hit.

The impact of this change when processing changegroup additions is
significant. On a generaldelta conversion of the "mozilla-unified"
repo (which contains heads of the main Firefox repositories in
chronological order - this means there are lots of transitions between
heads in revlog order), this change has the following impact when
performing an `hg unbundle` of an uncompressed bundle of the repo:

before: 5:42 CPU time
after:  4:34 CPU time

Most of this time is saved when applying the changelog and manifest
revlogs:

before: 2:30 CPU time
after:  1:17 CPU time

That nearly a 50% reduction in CPU time applying changesets and
manifests!

Applying a gzipped bundle of the same repo (effectively simulating a
`hg clone` over HTTP) showed a similar speedup:

before: 5:53 CPU time
after:  4:46 CPU time

Wall time improvements were basically the same as CPU time.

I didn't measure explicitly, but it feels like most of the time
is saved when processing manifests. This makes sense, as large
manifests tend to have very long delta chains and thus benefit the
most from this cache.

So, this change effectively makes changegroup application (which is
used by `hg unbundle`, `hg clone`, `hg pull`, `hg unshelve`, and
various other commands) significantly faster when delta chains are
long (which can happen on repos with large numbers of files and thus
large manifests).

In theory, this change can result in more memory utilization. However,
we're caching a dict of ints. At most we have 200 ints + Python object
overhead per revlog. And, the cache is really only populated when
performing read-heavy operations, such as adding changegroups or
scanning an individual revlog. For memory bloat to be an issue, we'd
need to scan/read several revisions from several revlogs all while
having active references to several revlogs. I don't think there are
many operations that do this, so I don't think memory bloat from the
cache will be an issue.

  $ cat >> $HGRCPATH <<EOF
  > [extensions]
  > rebase=
  > mq=
  > 
  > [phases]
  > publish=False
  > 
  > [alias]
  > tglog  = log -G --template "{rev}: '{desc}' {branches}\n"
  > theads = heads --template "{rev}: '{desc}' {branches}\n"
  > EOF

  $ hg init a
  $ cd a

  $ echo a > a
  $ hg ci -Am A
  adding a

  $ hg branch branch1
  marked working directory as branch branch1
  (branches are permanent and global, did you want a bookmark?)
  $ hg ci -m 'branch1'

  $ echo b > b
  $ hg ci -Am B
  adding b

  $ hg up -q 0

  $ hg branch branch2
  marked working directory as branch branch2
  $ hg ci -m 'branch2'

  $ echo c > C
  $ hg ci -Am C
  adding C

  $ hg up -q 2

  $ hg branch -f branch2
  marked working directory as branch branch2
  $ echo d > d
  $ hg ci -Am D
  adding d
  created new head

  $ echo e > e
  $ hg ci -Am E
  adding e

  $ hg update default
  0 files updated, 0 files merged, 3 files removed, 0 files unresolved

  $ hg branch branch3
  marked working directory as branch branch3
  $ hg ci -m 'branch3'

  $ echo f > f
  $ hg ci -Am F
  adding f

  $ cd ..


Rebase part of branch2 (5-6) onto branch3 (8):

  $ hg clone -q -u . a a1
  $ cd a1

  $ hg tglog
  @  8: 'F' branch3
  |
  o  7: 'branch3' branch3
  |
  | o  6: 'E' branch2
  | |
  | o  5: 'D' branch2
  | |
  | | o  4: 'C' branch2
  | | |
  +---o  3: 'branch2' branch2
  | |
  | o  2: 'B' branch1
  | |
  | o  1: 'branch1' branch1
  |/
  o  0: 'A'
  
  $ hg branches
  branch3                        8:4666b71e8e32
  branch2                        6:5097051d331d
  branch1                        2:0a03079c47fd (inactive)
  default                        0:1994f17a630e (inactive)

  $ hg theads
  8: 'F' branch3
  6: 'E' branch2
  4: 'C' branch2
  2: 'B' branch1
  0: 'A' 

  $ hg rebase -s 5 -d 8
  rebasing 5:635859577d0b "D"
  rebasing 6:5097051d331d "E"
  saved backup bundle to $TESTTMP/a1/.hg/strip-backup/635859577d0b-89160bff-backup.hg (glob)

  $ hg branches
  branch3                        8:466cdfb14b62
  branch2                        4:e4fdb121d036
  branch1                        2:0a03079c47fd
  default                        0:1994f17a630e (inactive)

  $ hg theads
  8: 'E' branch3
  4: 'C' branch2
  2: 'B' branch1
  0: 'A' 

  $ hg tglog
  o  8: 'E' branch3
  |
  o  7: 'D' branch3
  |
  @  6: 'F' branch3
  |
  o  5: 'branch3' branch3
  |
  | o  4: 'C' branch2
  | |
  | o  3: 'branch2' branch2
  |/
  | o  2: 'B' branch1
  | |
  | o  1: 'branch1' branch1
  |/
  o  0: 'A'
  
  $ cd ..


Rebase head of branch3 (8) onto branch2 (6):

  $ hg clone -q -u . a a2
  $ cd a2

  $ hg tglog
  @  8: 'F' branch3
  |
  o  7: 'branch3' branch3
  |
  | o  6: 'E' branch2
  | |
  | o  5: 'D' branch2
  | |
  | | o  4: 'C' branch2
  | | |
  +---o  3: 'branch2' branch2
  | |
  | o  2: 'B' branch1
  | |
  | o  1: 'branch1' branch1
  |/
  o  0: 'A'
  
  $ hg rebase -s 8 -d 6
  rebasing 8:4666b71e8e32 "F" (tip)
  saved backup bundle to $TESTTMP/a2/.hg/strip-backup/4666b71e8e32-fc1c4e96-backup.hg (glob)

  $ hg branches
  branch2                        8:6b4bdc1b5ac0
  branch3                        7:653b9feb4616
  branch1                        2:0a03079c47fd (inactive)
  default                        0:1994f17a630e (inactive)

  $ hg theads
  8: 'F' branch2
  7: 'branch3' branch3
  4: 'C' branch2
  2: 'B' branch1
  0: 'A' 

  $ hg tglog
  @  8: 'F' branch2
  |
  | o  7: 'branch3' branch3
  | |
  o |  6: 'E' branch2
  | |
  o |  5: 'D' branch2
  | |
  | | o  4: 'C' branch2
  | | |
  | | o  3: 'branch2' branch2
  | |/
  o |  2: 'B' branch1
  | |
  o |  1: 'branch1' branch1
  |/
  o  0: 'A'
  
  $ hg verify -q

  $ cd ..


Rebase entire branch3 (7-8) onto branch2 (6):

  $ hg clone -q -u . a a3
  $ cd a3

  $ hg tglog
  @  8: 'F' branch3
  |
  o  7: 'branch3' branch3
  |
  | o  6: 'E' branch2
  | |
  | o  5: 'D' branch2
  | |
  | | o  4: 'C' branch2
  | | |
  +---o  3: 'branch2' branch2
  | |
  | o  2: 'B' branch1
  | |
  | o  1: 'branch1' branch1
  |/
  o  0: 'A'
  
  $ hg rebase -s 7 -d 6
  rebasing 7:653b9feb4616 "branch3"
  note: rebase of 7:653b9feb4616 created no changes to commit
  rebasing 8:4666b71e8e32 "F" (tip)
  saved backup bundle to $TESTTMP/a3/.hg/strip-backup/653b9feb4616-3c88de16-backup.hg (glob)

  $ hg branches
  branch2                        7:6b4bdc1b5ac0
  branch1                        2:0a03079c47fd (inactive)
  default                        0:1994f17a630e (inactive)

  $ hg theads
  7: 'F' branch2
  4: 'C' branch2
  2: 'B' branch1
  0: 'A' 

  $ hg tglog
  @  7: 'F' branch2
  |
  o  6: 'E' branch2
  |
  o  5: 'D' branch2
  |
  | o  4: 'C' branch2
  | |
  | o  3: 'branch2' branch2
  | |
  o |  2: 'B' branch1
  | |
  o |  1: 'branch1' branch1
  |/
  o  0: 'A'
  
  $ hg verify -q

Stripping multiple branches in one go bypasses the fast-case code to
update the branch cache.

  $ hg strip 2
  0 files updated, 0 files merged, 4 files removed, 0 files unresolved
  saved backup bundle to $TESTTMP/a3/.hg/strip-backup/0a03079c47fd-11b7c407-backup.hg (glob)

  $ hg tglog
  o  3: 'C' branch2
  |
  o  2: 'branch2' branch2
  |
  | @  1: 'branch1' branch1
  |/
  o  0: 'A'
  

  $ hg branches
  branch2                        3:e4fdb121d036
  branch1                        1:63379ac49655
  default                        0:1994f17a630e (inactive)

  $ hg theads
  3: 'C' branch2
  1: 'branch1' branch1
  0: 'A' 

Fast path branchcache code should not be invoked if branches stripped is not
the same as branches remaining.

  $ hg init b
  $ cd b

  $ hg branch branch1
  marked working directory as branch branch1
  (branches are permanent and global, did you want a bookmark?)
  $ hg ci -m 'branch1'

  $ hg branch branch2
  marked working directory as branch branch2
  $ hg ci -m 'branch2'

  $ hg branch -f branch1
  marked working directory as branch branch1

  $ echo a > A
  $ hg ci -Am A
  adding A
  created new head

  $ hg tglog
  @  2: 'A' branch1
  |
  o  1: 'branch2' branch2
  |
  o  0: 'branch1' branch1
  

  $ hg theads
  2: 'A' branch1
  1: 'branch2' branch2

  $ hg strip 2
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  saved backup bundle to $TESTTMP/a3/b/.hg/strip-backup/a5b4b27ed7b4-a3b6984e-backup.hg (glob)

  $ hg theads
  1: 'branch2' branch2
  0: 'branch1' branch1


Make sure requesting to strip a revision already stripped does not confuse things.
Try both orders.

  $ cd ..

  $ hg init c
  $ cd c

  $ echo a > a
  $ hg ci -Am A
  adding a
  $ echo b > b
  $ hg ci -Am B
  adding b
  $ echo c > c
  $ hg ci -Am C
  adding c
  $ echo d > d
  $ hg ci -Am D
  adding d
  $ echo e > e
  $ hg ci -Am E
  adding e

  $ hg tglog
  @  4: 'E'
  |
  o  3: 'D'
  |
  o  2: 'C'
  |
  o  1: 'B'
  |
  o  0: 'A'
  

  $ hg strip 3 4
  0 files updated, 0 files merged, 2 files removed, 0 files unresolved
  saved backup bundle to $TESTTMP/a3/c/.hg/strip-backup/67a385d4e6f2-b9243789-backup.hg (glob)

  $ hg theads
  2: 'C' 

  $ hg strip 2 1
  0 files updated, 0 files merged, 2 files removed, 0 files unresolved
  saved backup bundle to $TESTTMP/a3/c/.hg/strip-backup/6c81ed0049f8-a687065f-backup.hg (glob)

  $ hg theads
  0: 'A' 

Make sure rebase does not break for phase/filter related reason
----------------------------------------------------------------
(issue3858)

  $ cd ..

  $ cat >> $HGRCPATH << EOF
  > [ui]
  > logtemplate={rev} {desc} {phase}\n
  > EOF


  $ hg init c4
  $ cd c4

  $ echo a > a
  $ hg ci -Am A
  adding a
  $ echo b > b
  $ hg ci -Am B
  adding b
  $ hg up 0
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ echo c > c
  $ hg ci -Am C
  adding c
  created new head
  $ hg up 1
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ hg merge
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg ci -m d
  $ hg up 2
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ echo e > e
  $ hg ci -Am E
  adding e
  created new head
  $ hg merge 3
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg ci -m F
  $ hg up 3
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ echo g > g
  $ hg ci -Am G
  adding g
  created new head
  $ echo h > h
  $ hg ci -Am H
  adding h
  $ hg up 5
  1 files updated, 0 files merged, 2 files removed, 0 files unresolved
  $ echo i > i
  $ hg ci -Am I
  adding i

Turn most changeset public

  $ hg ph -p 7

  $ hg heads
  8 I draft
  7 H public
  $ hg log -G
  @  8 I draft
  |
  | o  7 H public
  | |
  | o  6 G public
  | |
  o |  5 F draft
  |\|
  o |  4 E draft
  | |
  | o  3 d public
  |/|
  o |  2 C public
  | |
  | o  1 B public
  |/
  o  0 A public
  

  $ cat > $TESTTMP/checkeditform.sh <<EOF
  > env | grep HGEDITFORM
  > true
  > EOF
  $ HGEDITOR="sh $TESTTMP/checkeditform.sh" hg rebase --dest 7 --source 5 -e
  rebasing 5:361a99976cc9 "F"
  HGEDITFORM=rebase.merge
  rebasing 8:326cfedc031c "I" (tip)
  HGEDITFORM=rebase.normal
  saved backup bundle to $TESTTMP/a3/c4/.hg/strip-backup/361a99976cc9-35e980d0-backup.hg (glob)