From 7a56747a2c59442ae6d8611a58099404b9e196ae Mon Sep 17 00:00:00 2001
From: Pablo Galindo Salgado <pablogsal@gmail.com>
Date: Sat, 11 Jul 2026 16:51:51 +0100
Subject: [PATCH] gh-153568: Pause the GC while converting the AST to Python
 objects

Freshly converted AST nodes cannot be part of a reference cycle yet, so
collections during the conversion only pay to traverse the half-built
tree without ever freeing any of it.
---
 .../2026-07-11-16-51-51.gh-issue-153568.ast2objgc.rst     | 2 ++
 Parser/asdl_c.py                                          | 8 ++++++++
 Python/Python-ast.c                                       | 8 ++++++++
 3 files changed, 18 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Core_and_Builtins/2026-07-11-16-51-51.gh-issue-153568.ast2objgc.rst

diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2026-07-11-16-51-51.gh-issue-153568.ast2objgc.rst b/Misc/NEWS.d/next/Core_and_Builtins/2026-07-11-16-51-51.gh-issue-153568.ast2objgc.rst
new file mode 100644
index 000000000000000..b7d413d422994ff
--- /dev/null
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2026-07-11-16-51-51.gh-issue-153568.ast2objgc.rst
@@ -0,0 +1,2 @@
+Speed up :func:`ast.parse` by pausing the garbage collector while the AST is
+converted to Python objects.
diff --git a/Parser/asdl_c.py b/Parser/asdl_c.py
index d53886866f54f86..f409f32e6313589 100755
--- a/Parser/asdl_c.py
+++ b/Parser/asdl_c.py
@@ -2117,7 +2117,15 @@ class PartingShots(StaticVisitor):
     if (state == NULL) {
         return NULL;
     }
+    // Freshly converted AST nodes cannot be part of a reference cycle yet,
+    // so a garbage collection while building them cannot free anything of
+    // this tree and only pays to traverse its half-built nodes. Pause the
+    // collector while the conversion runs.
+    int gc_was_enabled = PyGC_Disable();
     PyObject *result = ast2obj_mod(state, t);
+    if (gc_was_enabled) {
+        PyGC_Enable();
+    }
 
     return result;
 }
diff --git a/Python/Python-ast.c b/Python/Python-ast.c
index f36072dfce098c6..aa1e5bc813b162f 100644
--- a/Python/Python-ast.c
+++ b/Python/Python-ast.c
@@ -18544,7 +18544,15 @@ PyObject* PyAST_mod2obj(mod_ty t)
     if (state == NULL) {
         return NULL;
     }
+    // Freshly converted AST nodes cannot be part of a reference cycle yet,
+    // so a garbage collection while building them cannot free anything of
+    // this tree and only pays to traverse its half-built nodes. Pause the
+    // collector while the conversion runs.
+    int gc_was_enabled = PyGC_Disable();
     PyObject *result = ast2obj_mod(state, t);
+    if (gc_was_enabled) {
+        PyGC_Enable();
+    }
 
     return result;
 }