AOT Map changes during production run

[Andrew Dinn]

On 09/10/2025 20:25, Ashutosh Mehra wrote:
> I am able to reproduce the problem Maria is seeing.
> Digging deeper it looks like when the map is generated during the 
> production run, the VM skips classes loaded by the custom loaders.
> VM gets the list of classes using 
> SystemDictionaryShared::get_all_archived_classes <https://github.com/ 
> openjdk/jdk/blob/1992b69a4794d1f2f65eaeb6dbb1e1e23a948b6e/src/hotspot/ 
> share/classfile/systemDictionaryShared.cpp#L1419-L1423> which only 
> iterates through the classes loaded by built-in loaders.
> With the following patch, I am able to get all the classes in the map 
> file generated in the prod run:
> 
> diff --git a/src/hotspot/share/classfile/systemDictionaryShared.cpp b/ 
> src/hotspot/share/classfile/systemDictionaryShared.cpp
> index b092e71f4e7..7e71dbefbfb 100644
> --- a/src/hotspot/share/classfile/systemDictionaryShared.cpp
> +++ b/src/hotspot/share/classfile/systemDictionaryShared.cpp
> @@ -1420,6 +1420,9 @@ void 
> SystemDictionaryShared::get_all_archived_classes(bool is_static_archive, Gr
>     get_archive(is_static_archive)->_builtin_dictionary.iterate([&] 
> (const RunTimeClassInfo* record) {
>         classes->append(record->klass());
>       });
> +  get_archive(is_static_archive)->_unregistered_dictionary.iterate([&] 
> (const RunTimeClassInfo* record) {
> +    classes->append(record->klass());
> +  });
>   }
> 
>   class SharedDictionaryPrinter : StackObj {
> 
> @Ioi Lam <mailto:ioi.lam at oracle.com> Do you think we should do this?

I am not sure if your patch is exactly what we want -- Ioi needs to 
answer that. However, I think it is important that the map file shows 
*all* the metadata that resides in the archive, including any metadata 
Klass and related structures that arecan be loaded via the unregistered 
dictionary.

This will be metadata for an app class that was not loaded via the 
bootstrap, module or system loader and hence one that cannot be 
associated with AOT linkage, profile data or compiled code. 
Nevertheless, the presence of a Klass and associated Method/ConstMethod 
+ field data means that loading of the class in a production run can 
bypass all the bytecode processing normally needed to create that 
metadata. The user needs to be able to observe that this basic level of 
optimization is still available via the AOT cache i.e. that they still 
retain the benefits that were present under CDS even though the extra 
AOT benefits are ruled out.

regards,


Andrew Dinn
-----------