AOT Map changes during production run

[María Arias de Reyna Dominguez]

Hi!

With this patch, it shows more elements than before, but still, training
data is suspiciously disappearing: MethodCounters, MethodData,
MethodTrainingData, and KlassTrainingData. Most of the Adapters are gone
too along with some TypeArrays and a few Symbols.

Cheers!
María. <ariasdereyna at redhat.com>


On Mon, Oct 13, 2025 at 12:01 PM Andrew Dinn <adinn at redhat.com> wrote:

> 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
> -----------
>
>
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