view tests/test-issue3084.t @ 47010:76ae43d5b1db stable

repoview: fix memory leak of filtered repo classes

The leak occurs in long-running server processes with
extensions, and is measured at 110kB per request.

Before this change, the contents of the `_filteredrepotypes`
cache are not properly garbage collected, despite it begin
a `WeakKeyDictionary`.

Extensions have a tendency to generate a new repository class
for each `localrepo` instantiation. Server processes based
on `hgwebdir_mod` will instantiate a new `localrepo` for each
HTTP request that involves a repository.

As a result, with a testing process that repeatedly opens a
repository with several extensions activated
(`topic` notably among them), we see a steady increase in
resident memory of 110kB per repository instantiation before this
change. This is also true, if we call `gc.collect()` at each
instantiation, like `hgwebdir_mod` does, or not.

The cause of the leak is that the *values* aren't weak references.
This change uses `weakref.ref` for the values, and this makes
in our measurements the resident size increase drop to 5kB per
repository instantiation, with no explicit call of `gc.collect()`
at all.
There is currently no reason to believe that this remaining leak
of 5kB is related to or even due to Mercurial core.

We've also seen evidence that `ui.ui` instances weren't properly
garbage collected before the change (with the change, they are).
This could explain why the figures are relatively high.

In theory, the collection of weak references could lead to
much more misses in the cache, so we measured the impact on
the original case that was motivation for introducing that cache
in 7e89bd0cfb86 (see also issue5043): `hg convert` of the
mozilla-central repository. The bad news here is that there is a
major memory leak there, both with and without the present changeset.
There were no more cache misses, and we could see no
more memory leak with this change: the resident size after importing
roughly 100000 changesets was at 12.4GB before, and 12.5GB after.
The small increase is mentioned for completeness only, and we
believe that it should be ignored, at least as long as the main
leak isn't fixed. At less than 1% of the main leak, even finding out
whether it is merely noise would be wasteful.

Original context where this was spotted and first mitigated:
  https://foss.heptapod.net/heptapod/heptapod/-/issues/466

The leak reduction was also obtained in Heptapod inner HTTP server,
which amounts to the same as `hgwebdir_mod` for these questions.

The measurements done with Python 3.9, similar figures seen with 3.8.
More work on our side would be needed to give measurements with 2.7,
because of testing server process does not support it.

  $ echo "[extensions]" >> $HGRCPATH
  $ echo "largefiles =" >> $HGRCPATH

Create the repository outside $HOME since largefiles write to
$HOME/.cache/largefiles.

  $ hg init test
  $ cd test
  $ echo "root" > root
  $ hg add root
  $ hg commit -m "Root commit" --config extensions.largefiles=!

Ensure that .hg/largefiles isn't created before largefiles are added
#if unix-permissions
  $ chmod 555 .hg
#endif
  $ hg status
#if unix-permissions
  $ chmod 755 .hg
#endif

  $ test -f .hg/largefiles
  [1]

  $ echo "large" > foo
  $ hg add --large foo
  $ hg commit -m "Add foo as a largefile"

  $ hg update -r 0
  getting changed largefiles
  0 largefiles updated, 1 removed
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved

  $ echo "normal" > foo
  $ hg add foo
  $ hg commit -m "Add foo as normal file"
  created new head

Normal file in the working copy, keeping the normal version:

  $ echo "n" | hg merge --config ui.interactive=Yes
  remote turned local normal file foo into a largefile
  use (l)argefile or keep (n)ormal file? n
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)

  $ hg status
  $ cat foo
  normal

Normal file in the working copy, keeping the largefile version:

  $ hg update -q -C
  $ echo "l" | hg merge --config ui.interactive=Yes
  remote turned local normal file foo into a largefile
  use (l)argefile or keep (n)ormal file? l
  getting changed largefiles
  1 largefiles updated, 0 removed
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  (branch merge, don't forget to commit)

  $ hg status
  M foo

  $ hg diff --nodates
  diff -r fa129ab6b5a7 .hglf/foo
  --- /dev/null
  +++ b/.hglf/foo
  @@ -0,0 +1,1 @@
  +7f7097b041ccf68cc5561e9600da4655d21c6d18
  diff -r fa129ab6b5a7 foo
  --- a/foo
  +++ /dev/null
  @@ -1,1 +0,0 @@
  -normal

  $ cat foo
  large

Largefile in the working copy, keeping the normal version:

  $ hg update -q -C -r 1
  $ echo "n" | hg merge --config ui.interactive=Yes
  remote turned local largefile foo into a normal file
  keep (l)argefile or use (n)ormal file? n
  getting changed largefiles
  0 largefiles updated, 0 removed
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  (branch merge, don't forget to commit)

  $ hg status
  M foo

  $ hg diff --nodates
  diff -r ff521236428a .hglf/foo
  --- a/.hglf/foo
  +++ /dev/null
  @@ -1,1 +0,0 @@
  -7f7097b041ccf68cc5561e9600da4655d21c6d18
  diff -r ff521236428a foo
  --- /dev/null
  +++ b/foo
  @@ -0,0 +1,1 @@
  +normal

  $ cat foo
  normal

Largefile in the working copy, keeping the largefile version:

  $ hg update -q -C -r 1
  $ echo "l" | hg merge --config ui.interactive=Yes
  remote turned local largefile foo into a normal file
  keep (l)argefile or use (n)ormal file? l
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)

  $ hg status

  $ cat foo
  large

Whatever ... commit something so we can invoke merge when updating

  $ hg commit -m '3: Merge'

Updating from largefile to normal - no reason to prompt

  $ hg up -r 2
  getting changed largefiles
  0 largefiles updated, 0 removed
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ cat foo
  normal

(the update above used to leave the working dir in a very weird state - clean it
  $ hg up -qr null
  $ hg up -qr 2
)

Updating from normal to largefile - no reason to prompt

  $ hg up -r 3
  getting changed largefiles
  1 largefiles updated, 0 removed
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ cat foo
  large

  $ cd ..


Systematic testing of merges involving largefiles:

Ancestor: normal  Parent: normal-id  Parent: large   result: large
Ancestor: normal  Parent: normal2    Parent: large   result: ?
Ancestor: large   Parent: large-id   Parent: normal  result: normal
Ancestor: large   Parent: large2     Parent: normal  result: ?

All cases should try merging both ways.

Prepare test repo:

  $ hg init merges
  $ cd merges

prepare cases with "normal" ancestor:

  $ hg up -qr null
  $ echo normal > f
  $ hg ci -Aqm "normal-ancestor"
  $ hg tag -l "normal-ancestor"
  $ touch f2
  $ hg ci -Aqm "normal-id"
  $ hg tag -l "normal-id"
  $ echo normal2 > f
  $ hg ci -m "normal2"
  $ hg tag -l "normal2"
  $ echo normal > f
  $ hg ci -Aqm "normal-same"
  $ hg tag -l "normal-same"
  $ hg up -qr "normal-ancestor"
  $ hg rm f
  $ echo large > f
  $ hg add --large f
  $ hg ci -qm "large"
  $ hg tag -l "large"

prepare cases with "large" ancestor:

  $ hg up -qr null
  $ echo large > f
  $ hg add --large f
  $ hg ci -qm "large-ancestor"
  $ hg tag -l "large-ancestor"
  $ touch f2
  $ hg ci -Aqm "large-id"
  $ hg tag -l "large-id"
  $ echo large2 > f
  $ hg ci -m "large2"
  $ hg tag -l "large2"
  $ echo large > f
  $ hg ci -Aqm "large-same"
  $ hg tag -l "large-same"
  $ hg up -qr "large-ancestor"
  $ hg rm f
  $ echo normal > f
  $ hg ci -qAm "normal"
  $ hg tag -l "normal"

  $ hg log -GT '{tags}'
  @  normal tip
  |
  | o  large-same
  | |
  | o  large2
  | |
  | o  large-id
  |/
  o  large-ancestor
  
  o  large
  |
  | o  normal-same
  | |
  | o  normal2
  | |
  | o  normal-id
  |/
  o  normal-ancestor
  


Ancestor: normal  Parent: normal-id  Parent: large   result: large

  $ hg up -Cqr normal-id
  $ hg merge -r large
  getting changed largefiles
  1 largefiles updated, 0 removed
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ cat f
  large

swap

  $ hg up -Cqr large
  $ hg merge -r normal-id
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ cat f
  large

Ancestor: normal  Parent: normal-same  Parent: large   result: large

  $ hg up -Cqr normal-same
  $ hg merge -r large
  getting changed largefiles
  1 largefiles updated, 0 removed
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ cat f
  large

swap

  $ hg up -Cqr large
  $ hg merge -r normal-same
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ cat f
  large

Ancestor: normal  Parent: normal2  Parent: large   result: ?
(annoying extra prompt ... but it do not do any serious harm)

  $ hg up -Cqr normal2
  $ hg merge -r large
  remote turned local normal file f into a largefile
  use (l)argefile or keep (n)ormal file? l
  getting changed largefiles
  1 largefiles updated, 0 removed
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ cat f
  large

  $ hg up -Cqr normal2
  $ echo n | hg merge -r large --config ui.interactive=Yes
  remote turned local normal file f into a largefile
  use (l)argefile or keep (n)ormal file? n
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ cat f
  normal2

swap

  $ hg up -Cqr large
  $ hg merge -r normal2
  remote turned local largefile f into a normal file
  keep (l)argefile or use (n)ormal file? l
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ cat f
  large

  $ hg up -Cqr large
  $ echo n | hg merge -r normal2 --config ui.interactive=Yes
  remote turned local largefile f into a normal file
  keep (l)argefile or use (n)ormal file? n
  getting changed largefiles
  0 largefiles updated, 0 removed
  2 files updated, 0 files merged, 1 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ cat f
  normal2

Ancestor: large   Parent: large-id   Parent: normal  result: normal

  $ hg up -Cqr large-id
  $ hg merge -r normal
  getting changed largefiles
  0 largefiles updated, 0 removed
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ cat f
  normal

swap

  $ hg up -Cqr normal
  $ hg merge -r large-id
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ cat f
  normal

Ancestor: large   Parent: large-same   Parent: normal  result: normal

  $ hg up -Cqr large-same
  $ hg merge -r normal
  getting changed largefiles
  0 largefiles updated, 0 removed
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ cat f
  normal

swap

  $ hg up -Cqr normal
  $ hg merge -r large-same
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ cat f
  normal

Ancestor: large   Parent: large2   Parent: normal  result: ?
(annoying extra prompt ... but it do not do any serious harm)

  $ hg up -Cqr large2
  $ hg merge -r normal
  remote turned local largefile f into a normal file
  keep (l)argefile or use (n)ormal file? l
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ cat f
  large2

  $ hg up -Cqr large2
  $ echo n | hg merge -r normal --config ui.interactive=Yes
  remote turned local largefile f into a normal file
  keep (l)argefile or use (n)ormal file? n
  getting changed largefiles
  0 largefiles updated, 0 removed
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ cat f
  normal

swap

  $ hg up -Cqr normal
  $ hg merge -r large2
  remote turned local normal file f into a largefile
  use (l)argefile or keep (n)ormal file? l
  getting changed largefiles
  1 largefiles updated, 0 removed
  2 files updated, 0 files merged, 1 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ cat f
  large2

  $ hg up -Cqr normal
  $ echo n | hg merge -r large2 --config ui.interactive=Yes
  remote turned local normal file f into a largefile
  use (l)argefile or keep (n)ormal file? n
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ cat f
  normal

  $ cd ..