OsmAnd's map engine is mostly native C++. The hardened allocator wraps malloc for that native heap, where decoded tile geometry and texture buffers live during scroll. The Java side still uses ART's GC, so you get a split: the UI can feel fine while the native render path pays the hardened-allocator tax on every tile churn. That also matches why a Leaflet WebView (one heap model) can feel different from the same map data inside OsmAnd.

OsmAnd has a large legacy C++ codebase with a lot of memory corruption bugs. Many memory corruption bugs have been found and reported by GrapheneOS users. It isn't yet clear if the performance issues the OpenGL renderer has with hardened_malloc are caused by it making too many allocations or actual bugs.

The hardened_malloc configuration used by GrapheneOS is very security-oriented including using a quarantine for freed slab allocations and it could provide a toggle to use a more performance-oriented configuration for an app instead of only being able to use the default allocator instead.