rust-dirstatemap: don't read the dirstate when requesting parents
A future patch for issue 6303 reveals a big performance regression in the Rust
`DirstateMap` that reads the entire dirstate when requesting parents instead
of the first 40 bytes.
`perfdiscovery` gets a *significant* speedup (from 0.101 to 0.016) when applied
against said patch.
I'm assuming it has other performance benefits, but this is already a good
enough win.
Differential Revision: https://phab.mercurial-scm.org/D8513
--- a/mercurial/dirstate.py Thu May 14 10:24:52 2020 -0400
+++ b/mercurial/dirstate.py Mon May 11 16:44:11 2020 +0200
@@ -1743,10 +1743,23 @@
@propertycache
def _rustmap(self):
- self._rustmap = rustmod.DirstateMap(self._root)
+ """
+ Fills the Dirstatemap when called.
+ Use `self._inner_rustmap` if reading the dirstate is not necessary.
+ """
+ self._rustmap = self._inner_rustmap
self.read()
return self._rustmap
+ @propertycache
+ def _inner_rustmap(self):
+ """
+ Does not fill the Dirstatemap when called. This allows for
+ optimizations where only setting/getting the parents is needed.
+ """
+ self._inner_rustmap = rustmod.DirstateMap(self._root)
+ return self._inner_rustmap
+
@property
def copymap(self):
return self._rustmap.copymap()
@@ -1756,6 +1769,7 @@
def clear(self):
self._rustmap.clear()
+ self._inner_rustmap.clear()
self.setparents(nullid, nullid)
util.clearcachedproperty(self, b"_dirs")
util.clearcachedproperty(self, b"_alldirs")
@@ -1812,7 +1826,7 @@
st = b''
try:
- self._parents = self._rustmap.parents(st)
+ self._parents = self._inner_rustmap.parents(st)
except ValueError:
raise error.Abort(
_(b'working directory state appears damaged!')