add upgrade notes

Author: valentijnscholten

docs/content/en/open_source/upgrading/2.54.md

@@ -5,7 +5,20 @@ weight: -20250804
 description: Dropped support for DD_PARSER_EXCLUDE
 ---
 
+## Breaking change: `DD_PARSER_EXCLUDE` removed
+
 To simplify the management of the DefectDojo application, parser exclusions are no longer controlled via the environment variable DD_PARSER_EXCLUDE or application settings. This variable is now unsupported.
 From now on, you should use the active flag in the Test_Type model to enable or disable parsers. Only parsers associated with active Test_Type entries will be available for use.
 
-There are other instructions for upgrading to 2.54.x. Check the Release Notes for the contents of the release.
+## Import/reimport performance improvements
+
+DefectDojo 2.54.x includes performance improvements for importing and reimporting scan results, especially for large scans:
+
+- **Faster imports and reimports** due to fewer database queries and more bulk operations.
+- **Reduced database load** during reimport matching and post-processing (helps avoid slowdowns/timeouts under heavy scan volume).
+- **More efficient endpoint status updates** during reimport of dynamic findings.
+- **Less churn when updating vulnerability IDs**, avoiding unnecessary deletes/writes when nothing changed.
+
+No action is required after upgrading. (Optional tuning knobs exist via `DD_IMPORT_REIMPORT_MATCH_BATCH_SIZE` and `DD_IMPORT_REIMPORT_DEDUPE_BATCH_SIZE`.)
+
+There are other instructions for upgrading to 2.54.x. Check the Release Notes for the contents of the release: `https://github.com/DefectDojo/django-DefectDojo/releases/tag/2.54.0`