RFR: JDK-8318566: Heap walking functions should not use FilteredFieldStream

[Alex Menkov]

On Wed, 31 Jan 2024 23:24:22 GMT, Chris Plummer <cjplummer at openjdk.org> wrote:

>> FilteredFieldStream used by heap walking functions to iterate through klass/superclasses/interfaces fields are known to have poor performance (see [JDK-8317692](https://bugs.openjdk.org/browse/JDK-8317692) for details).
>> Heap walking API implementation is the last user of the klasses.
>> The fix reworks iteration through klass/superclasses/interfaces fields and drops FilteredFieldStream-related code.
>> Additionally removed/updated includes of reflectionUtils.hpp.
>> 
>> Testing:
>>   - tier1..4;
>>   - test/hotspot/jtreg/vmTestbase/nsk/jvmti (contains tests for different heap walking functions);
>>   - new test from #17580 (now the test runs several times faster).
>
> src/hotspot/share/prims/jvmtiTagMap.cpp line 453:
> 
>> 451:   InstanceKlass* super_klass = ik->java_super();
>> 452:   if (super_klass != nullptr) {
>> 453:     start_index += add_instance_fields(super_klass, start_index);
> 
> Does hotspot have any rules against potentially very deep recursion that can overflow the stack?

I looked at hotspot code and don't see "implementation limits" for level of inheritance, so it looks like a valid concern.
Need to reimplement this without recursion.

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PR Review Comment: https://git.openjdk.org/jdk/pull/17661#discussion_r1474976858