bpo-37448: Use radix tree for pymalloc address_in_range(). (GH-14474)

The radix tree approach is a relatively simple and memory sanitary
alternative to the old (slightly) unsanitary address_in_range().
To disable the radix tree map, set a preprocessor flag as follows:
-DWITH_PYMALLOC_RADIX_TREE=0.

Co-authored-by: Tim Peters <tim.peters@gmail.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/Misc/NEWS.d/next/Core and Builtins/2021-02-21-14-19-35.bpo-37448.btl7vO.rst b/Misc/NEWS.d/next/Core and Builtins/2021-02-21-14-19-35.bpo-37448.btl7vO.rst
new file mode 100644
index 0000000..fe771a5
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2021-02-21-14-19-35.bpo-37448.btl7vO.rst
@@ -0,0 +1,15 @@
+Add a radix tree based memory map to track in-use obmalloc arenas. Use to
+replace the old implementation of address_in_range(). The radix tree
+approach makes it easy to increase pool sizes beyond the OS page size.
+Boosting the pool and arena size allows obmalloc to handle a significantly
+higher percentage of requests from its ultra-fast paths.
+
+It also has the advantage of eliminating the memory unsanitary behavior of
+the previous address_in_range(). The old address_in_range() was marked with
+the annotations _Py_NO_SANITIZE_ADDRESS, _Py_NO_SANITIZE_THREAD, and
+_Py_NO_SANITIZE_MEMORY. Those annotations are no longer needed.
+
+To disable the radix tree map, set a preprocessor flag as follows:
+`-DWITH_PYMALLOC_RADIX_TREE=0`.
+
+Co-authored-by: Tim Peters <tim.peters@gmail.com>