_loader: Add __slots__ to loadelement, meta*, and friendsdanielsilverstone-ct/loader-depends-smearing

Since these classes are basically named tuples, give them __slots__
to speed them up.

Signed-off-by: Daniel Silverstone <daniel.silverstone@codethink.co.uk>

3 files changed, 43 insertions, 0 deletions

diff --git a/src/buildstream/_loader/loadelement.py b/src/buildstream/_loader/loadelement.py
index 9296acc50..abb29d228 100644
--- a/src/buildstream/_loader/loadelement.py
+++ b/src/buildstream/_loader/loadelement.py
@@ -51,12 +51,27 @@ class LoadElement():
     #    element (LoadElement): a LoadElement on which there is a dependency
     #    dep_type (str): the type of dependency this dependency link is
     class Dependency:
+
+        __slots__ = ('element', 'dep_type')
+
         def __init__(self, element, dep_type):
             self.element = element
             self.dep_type = dep_type
 
     _counter = count()
 
+    __slots__ = (
+        'node',
+        'name',
+        'full_name',
+        'deps',
+        'meta_done',
+        'node_id',
+        'dependencies',
+        '_loader',
+        '_dep_cache',
+    )
+
     def __init__(self, node, filename, loader):
 
         #
diff --git a/src/buildstream/_loader/metaelement.py b/src/buildstream/_loader/metaelement.py
index 45eb6f4d0..cda1c3434 100644
--- a/src/buildstream/_loader/metaelement.py
+++ b/src/buildstream/_loader/metaelement.py
@@ -22,6 +22,24 @@ from .. import _yaml
 
 class MetaElement():
 
+    __slots__ = (
+        'project',
+        'name',
+        'kind',
+        'provenance',
+        'sources',
+        'config',
+        'variables',
+        'environment',
+        'env_nocache',
+        'public',
+        'sandbox',
+        'build_dependencies',
+        'dependencies',
+        'first_pass',
+        'is_junction',
+    )
+
     # MetaElement()
     #
     # An abstract object holding data suitable for constructing an Element
diff --git a/src/buildstream/_loader/metasource.py b/src/buildstream/_loader/metasource.py
index da2c0e292..5cf7dc7ba 100644
--- a/src/buildstream/_loader/metasource.py
+++ b/src/buildstream/_loader/metasource.py
@@ -20,6 +20,16 @@
 
 class MetaSource():
 
+    __slots__ = (
+        'element_name',
+        'element_index',
+        'element_kind',
+        'kind',
+        'config',
+        'directory',
+        'first_pass',
+    )
+
     # MetaSource()
     #
     # An abstract object holding data suitable for constructing a Source