Free typechecker state and ASTs when they are no longer needed

Instead of hanging around to all of them for the entire run of the
process, free ASTs and typechecker state (especially the type map) as
soon as a module is finished being processing.

In order to have this work when generating fine-grained dependencies,
we need to produce fine-grained dependencies much earlier, so
BuildManager now has an `fg_deps` field.

In the daemon, only free typechecker state, since we want to keep ASTs
around to increase recheck speed. (A future change might use an LRU
cache to keep only some around.)

Author: msullivan

mypy/build.py

@@ -59,6 +59,7 @@
 from mypy.typestate import TypeState, reset_global_state
 from mypy.renaming import VariableRenameVisitor
 from mypy.config_parser import parse_mypy_comments
+from mypy.freetree import free_tree
 
 
 # Switch to True to produce debug output related to fine-grained incremental
@@ -471,6 +472,7 @@ class BuildManager:
       missing_modules: Set of modules that could not be imported encountered so far
       stale_modules:   Set of modules that needed to be rechecked (only used by tests)
       fg_deps_meta:    Metadata for fine-grained dependencies caches associated with modules
+      fg_deps:         A fine-grained dependency map
       version_id:      The current mypy version (based on commit id when possible)
       plugin:          Active mypy plugin(s)
       plugins_snapshot:
@@ -523,6 +525,11 @@ def __init__(self, data_dir: str,
         self.modules = {}  # type: Dict[str, MypyFile]
         self.missing_modules = set()  # type: Set[str]
         self.fg_deps_meta = {}  # type: Dict[str, FgDepMeta]
+        # fg_deps holds the dependencies of every module that has been
+        # processed. We store this in BuildManager so that we can compute
+        # dependencies as we go, which allows us to free ASTs and type information,
+        # saving a ton of memory on net.
+        self.fg_deps = {}  # type: Dict[str, Set[str]]
         # Always convert the plugin to a ChainedPlugin so that it can be manipulated if needed
         if not isinstance(plugin, ChainedPlugin):
             plugin = ChainedPlugin(options, [plugin])
@@ -894,32 +901,24 @@ def invert_deps(deps: Dict[str, Set[str]],
     return rdeps
 
 
-def generate_deps_for_cache(proto_deps: Dict[str, Set[str]],
-                            manager: BuildManager,
+def generate_deps_for_cache(manager: BuildManager,
                             graph: Graph) -> Dict[str, Dict[str, Set[str]]]:
     """Generate fine-grained dependencies into a form suitable for serializing.
 
-    This does a few things:
-    1. Computes all fine grained deps from modules that were processed
-    2. Splits fine-grained deps based on the module of the trigger
-    3. For each module we generated fine-grained deps for, load any previous
+    This does a couple things:
+    1. Splits fine-grained deps based on the module of the trigger
+    2. For each module we generated fine-grained deps for, load any previous
        deps and merge them in.
 
     Returns a dictionary from module ids to all dependencies on that
     module. Dependencies not associated with a module in the build will be
     associated with the nearest parent module that is in the build, or the
     fake module FAKE_ROOT_MODULE if none are.
     """
-    from mypy.server.update import merge_dependencies  # Lazy import to speed up startup
-
-    # Compute the full set of dependencies from everything we've processed.
-    deps = {}  # type: Dict[str, Set[str]]
-    things = [st.compute_fine_grained_deps() for st in graph.values() if st.tree] + [proto_deps]
-    for st_deps in things:
-        merge_dependencies(st_deps, deps)
+    from mypy.server.deps import merge_dependencies  # Lazy import to speed up startup
 
     # Split the dependencies out into based on the module that is depended on.
-    rdeps = invert_deps(deps, graph)
+    rdeps = invert_deps(manager.fg_deps, graph)
 
     # We can't just clobber existing dependency information, so we
     # load the deps for every module we've generated new dependencies
@@ -2172,6 +2171,16 @@ def finish_passes(self) -> None:
                                 typemap=self.type_map())
             manager.report_file(self.tree, self.type_map(), self.options)
 
+            self.update_fine_grained_deps(self.manager.fg_deps)
+            self.free_state()
+            if not manager.options.fine_grained_incremental and not manager.options.preserve_asts:
+                free_tree(self.tree)
+
+    def free_state(self) -> None:
+        if self._type_checker:
+            self._type_checker.reset()
+            self._type_checker = None
+
     def _patch_indirect_dependencies(self,
                                      module_refs: Set[str],
                                      type_map: Dict[Expression, Type]) -> None:
@@ -2206,6 +2215,13 @@ def compute_fine_grained_deps(self) -> Dict[str, Set[str]]:
                                 python_version=self.options.python_version,
                                 options=self.manager.options)
 
+    def update_fine_grained_deps(self, deps: Dict[str, Set[str]]) -> None:
+        options = self.manager.options
+        if options.cache_fine_grained or options.fine_grained_incremental:
+            from mypy.server.deps import merge_dependencies  # Lazy import to speed up startup
+            merge_dependencies(self.compute_fine_grained_deps(), deps)
+            TypeState.update_protocol_deps(deps)
+
     def valid_references(self) -> Set[str]:
         assert self.ancestors is not None
         valid_refs = set(self.dependencies + self.suppressed + self.ancestors)
@@ -2616,10 +2632,9 @@ def dispatch(sources: List[BuildSource],
             # then we need to collect fine grained protocol dependencies.
             # Since these are a global property of the program, they are calculated after we
             # processed the whole graph.
-            TypeState.update_protocol_deps()
+            TypeState.add_all_protocol_deps(manager.fg_deps)
             if not manager.options.fine_grained_incremental:
-                proto_deps = TypeState.proto_deps or {}
-                rdeps = generate_deps_for_cache(proto_deps, manager, graph)
+                rdeps = generate_deps_for_cache(manager, graph)
                 write_deps_cache(rdeps, manager, graph)
 
     if manager.options.dump_deps:
@@ -3023,23 +3038,29 @@ def process_stale_scc(graph: Graph, scc: List[str], manager: BuildManager) -> No
             graph[id].semantic_analysis_pass_three()
         for id in stale:
             graph[id].semantic_analysis_apply_patches()
+
+    # Track what modules aren't yet done so we can finish them as soon
+    # as possible, saving memory.
+    unfinished_modules = set(stale)
     for id in stale:
         graph[id].type_check_first_pass()
-    more = True
-    while more:
-        more = False
+        if not graph[id].type_checker().deferred_nodes:
+            unfinished_modules.discard(id)
+            graph[id].finish_passes()
+
+    while unfinished_modules:
         for id in stale:
-            if graph[id].type_check_second_pass():
-                more = True
+            if id not in unfinished_modules:
+                continue
+            if not graph[id].type_check_second_pass():
+                unfinished_modules.discard(id)
+                graph[id].finish_passes()
     for id in stale:
         graph[id].generate_unused_ignore_notes()
     if any(manager.errors.is_errors_for_file(graph[id].xpath) for id in stale):
         for id in stale:
             graph[id].transitive_error = True
     for id in stale:
-        graph[id].finish_passes()
-        if manager.options.cache_fine_grained or manager.options.fine_grained_incremental:
-            graph[id].compute_fine_grained_deps()
         manager.flush_errors(manager.errors.file_messages(graph[id].xpath), False)
         graph[id].write_cache()
         graph[id].mark_as_rechecked()

mypy/freetree.py

@@ -0,0 +1,14 @@
+"""Generic node traverser visitor"""
+
+from mypy.traverser import TraverserVisitor
+from mypy.nodes import Block, MypyFile
+
+
+class TreeFreer(TraverserVisitor):
+    def visit_block(self, block: Block) -> None:
+        super().visit_block(block)
+        block.body.clear()
+
+
+def free_tree(tree: MypyFile) -> None:
+    tree.accept(TreeFreer())

mypy/options.py

@@ -216,6 +216,12 @@ def __init__(self) -> None:
         # in modules being compiled. Not in the config file or command line.
         self.mypyc = False
 
+        # Disable the memory optimization of freeing ASTs when
+        # possible. This isn't exposed as a command line option
+        # because it is intended for software integrating with
+        # mypy. (Like mypyc.)
+        self.preserve_asts = False
+
         # Paths of user plugins
         self.plugins = []  # type: List[str]
 

mypy/server/deps.py

@@ -958,6 +958,12 @@ def visit_union_type(self, typ: UnionType) -> List[str]:
         return triggers
 
 
+def merge_dependencies(new_deps: Dict[str, Set[str]],
+                       deps: Dict[str, Set[str]]) -> None:
+    for trigger, targets in new_deps.items():
+        deps.setdefault(trigger, set()).update(targets)
+
+
 def non_trivial_bases(info: TypeInfo) -> List[TypeInfo]:
     return [base for base in info.mro[1:]
             if base.fullname() != 'builtins.object']

mypy/server/update.py

@@ -140,7 +140,7 @@
 from mypy.server.astmerge import merge_asts
 from mypy.server.aststrip import strip_target
 from mypy.server.aststripnew import strip_target_new, SavedAttributes
-from mypy.server.deps import get_dependencies_of_target
+from mypy.server.deps import get_dependencies_of_target, merge_dependencies
 from mypy.server.target import trigger_to_target
 from mypy.server.trigger import make_trigger, WILDCARD_TAG
 from mypy.util import module_prefix, split_target
@@ -163,7 +163,9 @@ def __init__(self, result: BuildResult) -> None:
         self.manager = manager
         self.graph = result.graph
         self.previous_modules = get_module_to_path_map(self.graph)
-        self.deps = get_all_dependencies(manager, self.graph)
+        self.deps = manager.fg_deps
+        # Merge in any root dependencies that may not have been loaded
+        merge_dependencies(manager.load_fine_grained_deps(FAKE_ROOT_MODULE), self.deps)
         self.previous_targets_with_errors = manager.errors.targets()
         self.previous_messages = result.errors[:]
         # Module, if any, that had blocking errors in the last run as (id, path) tuple.
@@ -378,7 +380,8 @@ def update_module(self,
             self.manager.log_fine_grained('triggered: %r' % sorted(filtered))
         self.triggered.extend(triggered | self.previous_targets_with_errors)
         if module in graph:
-            merge_dependencies(graph[module].compute_fine_grained_deps(), self.deps)
+            graph[module].update_fine_grained_deps(self.deps)
+            graph[module].free_state()
         remaining += propagate_changes_using_dependencies(
             manager, graph, self.deps, triggered,
             {module},
@@ -453,15 +456,11 @@ def ensure_trees_loaded(manager: BuildManager, graph: Dict[str, State],
         process_fresh_modules(graph, to_process, manager)
 
 
-def get_all_dependencies(manager: BuildManager, graph: Dict[str, State]) -> Dict[str, Set[str]]:
-    """Return the fine-grained dependency map for an entire build."""
-    # Deps for each module were computed during build() or loaded from the cache.
-    deps = manager.load_fine_grained_deps(FAKE_ROOT_MODULE)  # type: Dict[str, Set[str]]
-    for id in graph:
-        if graph[id].tree is not None:
-            merge_dependencies(graph[id].compute_fine_grained_deps(), deps)
-    TypeState.add_all_protocol_deps(deps)
-    return deps
+def fix_fg_dependencies(manager: BuildManager, deps: Dict[str, Set[str]]) -> None:
+    """Populate the dependencies with stuff that build may have missed"""
+    # This means the root module and typestate
+    merge_dependencies(manager.load_fine_grained_deps(FAKE_ROOT_MODULE), deps)
+    # TypeState.add_all_protocol_deps(deps)
 
 
 # The result of update_module_isolated when no blockers, with these items:
@@ -608,15 +607,12 @@ def restore(ids: List[str]) -> None:
     state.type_check_first_pass()
     state.type_check_second_pass()
     t2 = time.time()
-    state.compute_fine_grained_deps()
-    t3 = time.time()
     state.finish_passes()
-    t4 = time.time()
+    t3 = time.time()
     manager.add_stats(
         semanal_time=t1 - t0,
         typecheck_time=t2 - t1,
-        deps_time=t3 - t2,
-        finish_passes_time=t4 - t3)
+        finish_passes_time=t3 - t2)
 
     graph[module] = state
 
@@ -700,14 +696,6 @@ def get_sources(fscache: FileSystemCache,
     return sources
 
 
-def merge_dependencies(new_deps: Dict[str, Set[str]],
-                       deps: Dict[str, Set[str]]) -> None:
-    for trigger, targets in new_deps.items():
-        deps.setdefault(trigger, set()).update(targets)
-    # Merge also the newly added protocol deps.
-    TypeState.update_protocol_deps(deps)
-
-
 def calculate_active_triggers(manager: BuildManager,
                               old_snapshots: Dict[str, Dict[str, SnapshotItem]],
                               new_modules: Dict[str, Optional[MypyFile]]) -> Set[str]:
@@ -994,6 +982,8 @@ def key(node: FineGrainedDeferredNode) -> int:
     # Report missing imports.
     graph[module_id].verify_dependencies()
 
+    graph[module_id].free_state()
+
     return new_triggered
 
 

mypy/test/testdeps.py

@@ -45,6 +45,7 @@ def run_case(self, testcase: DataDrivenTestCase) -> None:
         options.cache_dir = os.devnull
         options.python_version = python_version
         options.export_types = True
+        options.preserve_asts = True
         messages, files, type_map = self.build(src, options)
         a = messages
         if files is None or type_map is None:

mypy/test/testmerge.py

@@ -106,6 +106,7 @@ def build(self, source: str, testcase: DataDrivenTestCase) -> Optional[BuildResu
         options.incremental = True
         options.fine_grained_incremental = True
         options.use_builtins_fixtures = True
+        options.export_types = True
         options.show_traceback = True
         options.python_version = PYTHON3_VERSION
         main_path = os.path.join(test_temp_dir, 'main')
@@ -216,7 +217,13 @@ def dump_types(self, manager: FineGrainedBuildManager) -> List[str]:
         for module_id in sorted(manager.manager.modules):
             if not is_dumped_module(module_id):
                 continue
-            type_map = manager.graph[module_id].type_map()
+            all_types = manager.manager.all_types
+            # Compute a module type map from the global type map
+            tree = manager.graph[module_id].tree
+            assert tree is not None
+            type_map = {node: all_types[node]
+                        for node in get_subexpressions(tree)
+                        if node in all_types}
             if type_map:
                 a.append('## {}'.format(module_id))
                 for expr in sorted(type_map, key=lambda n: (n.line, short_type(n),

mypy/test/testtypegen.py

@@ -31,6 +31,7 @@ def run_case(self, testcase: DataDrivenTestCase) -> None:
             options.use_builtins_fixtures = True
             options.show_traceback = True
             options.export_types = True
+            options.preserve_asts = True
             result = build.build(sources=[BuildSource('main', None, src)],
                                  options=options,
                                  alt_lib_path=test_temp_dir)

mypy/typestate.py

@@ -211,15 +211,13 @@ def update_protocol_deps(second_map: Optional[Dict[str, Set[str]]] = None) -> No
     def add_all_protocol_deps(deps: Dict[str, Set[str]]) -> None:
         """Add all known protocol dependencies to deps.
 
-        This is used by tests and debug output, and also when passing
-        all collected or loaded dependencies on to FineGrainedBuildManager
-        in its __init__.
+        This is used by tests and debug output, and also when collecting
+        all collected or loaded dependencies as part of build.
         """
         TypeState.update_protocol_deps()  # just in case
-        assert TypeState.proto_deps is not None, (
-            "This should not be called after failed cache load")
-        for trigger, targets in TypeState.proto_deps.items():
-            deps.setdefault(trigger, set()).update(targets)
+        if TypeState.proto_deps is not None:
+            for trigger, targets in TypeState.proto_deps.items():
+                deps.setdefault(trigger, set()).update(targets)
 
 
 def reset_global_state() -> None: