RFR: 8300926: Several startup regressions ~6-70% in 21-b6 all platforms [v4]

[Robbin Ehn]

On Fri, 24 Feb 2023 02:50:55 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> I think you are taking about CDS dump process. It works fine taking the lock.
>> I think this was just some micro-optimization. But we should not mark and do deopt fixed that.
>
> To restate: the assert_locked_or_safepoint is pointless because you just took out the lock here.
> 
> The code Dan points to does not seem to be related to CDS dump:
> 
> bool vmClasses::resolve(vmClassID id, TRAPS) {
>   InstanceKlass** klassp = &_klasses[as_int(id)];
> 
> #if INCLUDE_CDS
>   if (UseSharedSpaces && !JvmtiExport::should_post_class_prepare()) {
>     InstanceKlass* k = *klassp;
>     assert(k->is_shared_boot_class(), "must be");
> 
>     ClassLoaderData* loader_data = ClassLoaderData::the_null_class_loader_data();
>     resolve_shared_class(k, loader_data, Handle(), CHECK_false);
>     return true;
>   }
> #endif // INCLUDE_CDS
> 
> I remain concerned this code may be executed at a safepoint and we will now try to take the Compile_lock.

I did not find in testing any case that executed the add_to_hierarchy.
I'll check more!

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PR: https://git.openjdk.org/jdk/pull/12585