[PATCH 6 of 9 V4] manifest: change manifestlog mancache to be directory based

Martin von Zweigbergk martinvonz at google.com
Wed Sep 21 16:31:44 EDT 2016


On Tue, Sep 20, 2016 at 4:47 PM, Durham Goode <durham at fb.com> wrote:
> # HG changeset patch
> # User Durham Goode <durham at fb.com>
> # Date 1474415164 25200
> #      Tue Sep 20 16:46:04 2016 -0700
> # Node ID 69b91c12d904f329eff6618ac43f5cfef631e8dc
> # Parent  52a206d772021194ab4356aeba2c73650851a624
> manifest: change manifestlog mancache to be directory based
>
> In the last patch we added a get() function that allows fetching directory level
> treemanifestctxs. It didn't handle caching at directory level though, so we need to
> change our mancache to support multiple directories.
>
> diff --git a/mercurial/manifest.py b/mercurial/manifest.py
> --- a/mercurial/manifest.py
> +++ b/mercurial/manifest.py
> @@ -1021,9 +1021,16 @@ class manifestlog(object):
>              usetreemanifest = opts.get('treemanifest', usetreemanifest)
>          self._treeinmem = usetreemanifest
>
> +        # A dictionary containing the cache for each directory

nit: "dictionary" doesn't add much. I'd rather say what is cached
([tree]manifestctx instances, right?).

> +        self._dirmancache = {}
> +
>          # We'll separate this into it's own cache once oldmanifest is no longer
>          # used
> -        self._mancache = repo.manifest._mancache
> +        self._dirmancache[''] = repo.manifest._mancache

IIUC, the root manifest's cache will be shared, but subdirectory logs
will not be? I think the cache is not used very frequently, so maybe
it's not a big deal? Do you know a good test case for it? Rebase?
We're looking for a case where both manifest._mancache and
manifestlog._dirmancache will be used, right? Perhaps there are no
such cases so it doesn't matter? So it's probably fine, just wanted to
point it out in case you can think of problem that I did not see.

> +
> +        # A future patch makes this use the same config value as the existing
> +        # mancache
> +        self.cachesize = 4
>
>      @property
>      def _revlog(self):
> @@ -1039,6 +1046,14 @@ class manifestlog(object):
>          """Retrieves the manifest instance for the given node. Throws a KeyError
>          if not found.
>          """
> +        if node in self._dirmancache.get(dir, ()):
> +            cachemf = self._dirmancache[dir][node]
> +            # The old manifest may put non-ctx manifests in the cache, so
> +            # skip those since they don't implement the full api.
> +            if (isinstance(cachemf, manifestctx) or
> +                isinstance(cachemf, treemanifestctx)):
> +                return cachemf
> +
>          if dir:
>              if self._revlog._treeondisk:
>                  m = treemanifestctx(self._revlog.dirlog(dir), dir, node)
> @@ -1047,20 +1062,17 @@ class manifestlog(object):
>                          _("cannot ask for manifest directory '%s' in a flat "
>                            "manifest") % dir)
>          else:
> -            if node in self._mancache:
> -                cachemf = self._mancache[node]
> -                # The old manifest may put non-ctx manifests in the cache, so
> -                # skip those since they don't implement the full api.
> -                if (isinstance(cachemf, manifestctx) or
> -                    isinstance(cachemf, treemanifestctx)):
> -                    return cachemf
> -
>              if self._treeinmem:
>                  m = treemanifestctx(self._revlog, '', node)
>              else:
>                  m = manifestctx(self._revlog, node)
> -            if node != revlog.nullid:
> -                self._mancache[node] = m
> +
> +        if node != revlog.nullid:
> +            mancache = self._dirmancache.get(dir)
> +            if not mancache:
> +                mancache = util.lrucachedict(self.cachesize)
> +                self._dirmancache[dir] = mancache
> +            mancache[node] = m
>          return m
>
>      def add(self, m, transaction, link, p1, p2, added, removed):
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