Integrated: 8291718: Remove mark_for_deoptimization from klass unloading

[Axel Boldt-Christmas]

On Tue, 2 Aug 2022 14:30:07 GMT, Axel Boldt-Christmas <aboldtch at openjdk.org> wrote:

> @stefank suggested creating a separate issue for this part of [JDK-8291237](https://bugs.openjdk.org/browse/JDK-8291237) 
> 
> Description from the original issue: 
>> The klass unloading code currently sets the mark for deoptimzation flag on nmethods that depend on the klass being unloaded. That however is all it does, there is no guarantee that those nmethods will become not entrant and make_deoptimized. The current implementation may if some future deoptimization happens to trigger see these marks as it scans the whole code cache, but it is never triggered from klass unloading. 
>> 
>> Me and [~eosterlund] discussed this and this behaviour seems like some leftover from earlier versions of klass unloading. There should be no reason to eliminate the nmethods that depend on unloaded klasses except to eliminate dead code. It is probably better to let other mechanisms decide if an nmethod with dead code should be deoptimized than the klass unloading. 
>> 
>> It might be a future improvement to have some stats which record that an nmethod had some dependency to an unloaded klass which might effect the heuristic for selecting what methods are deoptimized.
> 
> Testing: Tier 1-7

This pull request has now been integrated.

Changeset: fd4b2f28
Author:    Axel Boldt-Christmas <aboldtch at openjdk.org>
Committer: Erik Österlund <eosterlund at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/fd4b2f2868ac6eaf192b50db5c5adc76e0d54308
Stats:     57 lines in 18 files changed: 21 ins; 16 del; 20 mod

8291718: Remove mark_for_deoptimization from klass unloading

Reviewed-by: eosterlund, dlong

-------------

PR: https://git.openjdk.org/jdk/pull/9713