[PATCH 7 of 7] context: floor adjustlinkrev graph walk during copy tracing

[Martin von Zweigbergk]

On Fri, Sep 7, 2018 at 8:14 AM Boris Feld <boris.feld at octobus.net> wrote:

> # HG changeset patch
> # User Boris Feld <boris.feld at octobus.net>
> # Date 1536255188 14400
> #      Thu Sep 06 13:33:08 2018 -0400
> # Node ID 0f720a4aa166d08daaa39e8462f2291f77e825c1
> # Parent  441c39342d63c75ee101587b2fbf3af60800762f
> # EXP-Topic copy-perf
> # Available At https://bitbucket.org/octobus/mercurial-devel/
> #              hg pull https://bitbucket.org/octobus/mercurial-devel/ -r
> 0f720a4aa166
> context: floor adjustlinkrev graph walk during copy tracing
>
> The `_adjustlinkrev` method gains an optional "floor" argument. The linkrev
> adjustment will give up once this floor is reached. The relevant functions
> using `_adjustlinkrev` are updated to pass an appropriate value in the copy
> tracing code.
>
> In some private repository, about 10% of the status call triggered
> pathological case addressed by this change. The speedup varies from one
> call
> to another, the best-observed win is moving from 170s to 11s.
>
> diff --git a/mercurial/context.py b/mercurial/context.py
> --- a/mercurial/context.py
> +++ b/mercurial/context.py
> @@ -633,7 +633,7 @@ class basefilectx(object):
>      def _changeid(self):
>          return self._findchangeid()
>
> -    def _findchangeid(self):
> +    def _findchangeid(self, floor=None):
>

Could we call it "stoprev" like we do in revlog.ancestors() and a few other
places (assuming it's conceptually the same thing)?

         if r'_changeid' in self.__dict__:
>              changeid = self._changeid
>          elif r'_changectx' in self.__dict__:
> @@ -641,10 +641,11 @@ class basefilectx(object):
>          elif r'_descendantrev' in self.__dict__:
>              # this file context was created from a revision with a known
>              # descendant, we can (lazily) correct for linkrev aliases
> -            changeid = self._adjustlinkrev(self._descendantrev)
> +            changeid = self._adjustlinkrev(self._descendantrev,
> floor=floor)
>          else:
>              changeid = self._filelog.linkrev(self._filerev)
> -        self._changeid = changeid
> +        if changeid is not None:
> +            self._changeid = changeid
>          return changeid
>
>      @propertycache
> @@ -788,7 +789,7 @@ class basefilectx(object):
>
>          return True
>
> -    def _adjustlinkrev(self, srcrev, inclusive=False):
> +    def _adjustlinkrev(self, srcrev, inclusive=False, floor=None):
>          """return the first ancestor of <srcrev> introducing <fnode>
>
>          If the linkrev of the file revision does not point to an ancestor
> of
> @@ -797,6 +798,10 @@ class basefilectx(object):
>
>          :srcrev: the changeset revision we search ancestors from
>          :inclusive: if true, the src revision will also be checked
> +        :floor: an optional revision to stop the walk at. If no
> introduction
> +                of this file content could be found before this floor
> +                revision, the function will returns "None" and stops its
> +                iteration.
>          """
>          repo = self._repo
>          cl = repo.unfiltered().changelog
> @@ -822,6 +827,8 @@ class basefilectx(object):
>              fnode = self._filenode
>              path = self._path
>              for a in iteranc:
> +                if floor is not None and a < floor:
> +                    return None
>                  ac = cl.read(a) # get changeset data (we avoid object
> creation)
>                  if path in ac[3]: # checking the 'files' field.
>                      # The file has been touched, check if the content is
> @@ -837,8 +844,12 @@ class basefilectx(object):
>      def isintroducedafter(self, changelogrev):
>          """True if a filectx have been introduced after a given floor
> revision
>          """
> -        return (changelogrev <= self.linkrev()
> -                or changelogrev <= self._introrev())
> +        if changelogrev <= self.linkrev():
> +            return True
> +        introrev = self._introrev(floor=changelogrev)
> +        if introrev is None:
> +            return False
> +        return changelogrev <= introrev
>
>      def _lazyrev(self):
>          """return self.rev() if it is available without computation,
> @@ -865,19 +876,28 @@ class basefilectx(object):
>          revision is one of its ancestors. This prevents bugs from
>          'linkrev-shadowing' when a file revision is used by multiple
>          changesets.
> +
>

Seems accidental and should be dropped?


>          """
>          return self._introrev()
>
> -    def _introrev(self):
> +    def _introrev(self, floor=None):
> +        """
> +        Same as `introrev` but, with an extra argument to limit changelog
> +        iteration range in some internal usecase.
> +
> +        If `floor` is set, the `introrev` will not be searched past that
> +        `floor` revision and "None" might be returned. This is useful to
> limit
> +        iteration range.
> +        """
>          lkr = self.linkrev()
>          lazyrev = self._lazyrev()
>          if lazyrev is not None:
>              if lazyrev == lkr:
>                  return lazyrev
>              else:
> -                return self._adjustlinkrev(lazyrev, inclusive=True)
> +                return self._adjustlinkrev(lazyrev, inclusive=True,
> floor=floor)
>          else:
> -            return self._findchangeid()
> +            return self._findchangeid(floor=floor)
>
>      def introfilectx(self):
>          """Return filectx having identical contents, but pointing to the
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