gh-113141: Tune MI_SEGMENT_SLICE_SHIFT to 14 for using 16 Kib pages

Author: corona10

Include/internal/pycore_mimalloc.h

@@ -32,6 +32,9 @@ typedef enum {
 #  define MI_NO_THP 1
 // Do not use guarded allocations. The free-threaded GC does not support their block layout.
 #  define MI_GUARDED 0
+// Use 16 KiB pages instead of 64 KiB pages. 
+// Original value was 16.
+#  define MI_SEGMENT_SLICE_SHIFT 14
 #ifdef Py_DEBUG
 #  define MI_DEBUG 2
 #else