Mercurial > hg
view tests/test-help-hide.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.
| author | Georges Racinet <georges.racinet@octobus.net> |
|---|---|
| date | Fri, 23 Apr 2021 18:30:53 +0200 |
| parents | bb3a5c0df06b |
| children | da4e6d7a8fdd |
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Test hiding some commands (which also happens to hide an entire category). $ hg --config help.hidden-command.clone=true \ > --config help.hidden-command.init=true help Mercurial Distributed SCM list of commands: Remote repository management: incoming show new changesets found in source outgoing show changesets not found in the destination paths show aliases for remote repositories pull pull changes from the specified source push push changes to the specified destination serve start stand-alone webserver Change creation: commit commit the specified files or all outstanding changes Change manipulation: backout reverse effect of earlier changeset graft copy changes from other branches onto the current branch merge merge another revision into working directory Change organization: bookmarks create a new bookmark or list existing bookmarks branch set or show the current branch name branches list repository named branches phase set or show the current phase name tag add one or more tags for the current or given revision tags list repository tags File content management: annotate show changeset information by line for each file cat output the current or given revision of files copy mark files as copied for the next commit diff diff repository (or selected files) grep search for a pattern in specified files Change navigation: bisect subdivision search of changesets heads show branch heads identify identify the working directory or specified revision log show revision history of entire repository or files Working directory management: add add the specified files on the next commit addremove add all new files, delete all missing files files list tracked files forget forget the specified files on the next commit purge removes files not tracked by Mercurial remove remove the specified files on the next commit rename rename files; equivalent of copy + remove resolve redo merges or set/view the merge status of files revert restore files to their checkout state root print the root (top) of the current working directory shelve save and set aside changes from the working directory status show changed files in the working directory summary summarize working directory state unshelve restore a shelved change to the working directory update update working directory (or switch revisions) Change import/export: archive create an unversioned archive of a repository revision bundle create a bundle file export dump the header and diffs for one or more changesets import import an ordered set of patches unbundle apply one or more bundle files Repository maintenance: manifest output the current or given revision of the project manifest recover roll back an interrupted transaction verify verify the integrity of the repository Help: config show combined config settings from all hgrc files help show help for a given topic or a help overview version output version and copyright information additional help topics: Mercurial identifiers: filesets Specifying File Sets hgignore Syntax for Mercurial Ignore Files patterns File Name Patterns revisions Specifying Revisions urls URL Paths Mercurial output: color Colorizing Outputs dates Date Formats diffs Diff Formats templating Template Usage Mercurial configuration: config Configuration Files environment Environment Variables extensions Using Additional Features flags Command-line flags hgweb Configuring hgweb merge-tools Merge Tools pager Pager Support Concepts: bundlespec Bundle File Formats glossary Glossary phases Working with Phases subrepos Subrepositories Miscellaneous: deprecated Deprecated Features internals Technical implementation topics scripting Using Mercurial from scripts and automation (use 'hg help -v' to show built-in aliases and global options) Test hiding some topics. $ hg --config help.hidden-topic.deprecated=true \ > --config help.hidden-topic.internals=true \ > --config help.hidden-topic.scripting=true help Mercurial Distributed SCM list of commands: Repository creation: clone make a copy of an existing repository init create a new repository in the given directory Remote repository management: incoming show new changesets found in source outgoing show changesets not found in the destination paths show aliases for remote repositories pull pull changes from the specified source push push changes to the specified destination serve start stand-alone webserver Change creation: commit commit the specified files or all outstanding changes Change manipulation: backout reverse effect of earlier changeset graft copy changes from other branches onto the current branch merge merge another revision into working directory Change organization: bookmarks create a new bookmark or list existing bookmarks branch set or show the current branch name branches list repository named branches phase set or show the current phase name tag add one or more tags for the current or given revision tags list repository tags File content management: annotate show changeset information by line for each file cat output the current or given revision of files copy mark files as copied for the next commit diff diff repository (or selected files) grep search for a pattern in specified files Change navigation: bisect subdivision search of changesets heads show branch heads identify identify the working directory or specified revision log show revision history of entire repository or files Working directory management: add add the specified files on the next commit addremove add all new files, delete all missing files files list tracked files forget forget the specified files on the next commit purge removes files not tracked by Mercurial remove remove the specified files on the next commit rename rename files; equivalent of copy + remove resolve redo merges or set/view the merge status of files revert restore files to their checkout state root print the root (top) of the current working directory shelve save and set aside changes from the working directory status show changed files in the working directory summary summarize working directory state unshelve restore a shelved change to the working directory update update working directory (or switch revisions) Change import/export: archive create an unversioned archive of a repository revision bundle create a bundle file export dump the header and diffs for one or more changesets import import an ordered set of patches unbundle apply one or more bundle files Repository maintenance: manifest output the current or given revision of the project manifest recover roll back an interrupted transaction verify verify the integrity of the repository Help: config show combined config settings from all hgrc files help show help for a given topic or a help overview version output version and copyright information additional help topics: Mercurial identifiers: filesets Specifying File Sets hgignore Syntax for Mercurial Ignore Files patterns File Name Patterns revisions Specifying Revisions urls URL Paths Mercurial output: color Colorizing Outputs dates Date Formats diffs Diff Formats templating Template Usage Mercurial configuration: config Configuration Files environment Environment Variables extensions Using Additional Features flags Command-line flags hgweb Configuring hgweb merge-tools Merge Tools pager Pager Support Concepts: bundlespec Bundle File Formats glossary Glossary phases Working with Phases subrepos Subrepositories (use 'hg help -v' to show built-in aliases and global options)