RFR: 8316632: Shenandoah: Raise OOME when gc threshold is exceeded

[Y. Srinivas Ramakrishna]

On Thu, 21 Sep 2023 22:08:32 GMT, William Kemper <wkemper at openjdk.org> wrote:

>> src/hotspot/share/gc/shenandoah/shenandoahHeap.cpp line 947:
>> 
>>> 945:     control_thread()->handle_alloc_failure(req, false);
>>> 946:     notify_gc_progress();
>>> 947:     *gc_overhead_limit_was_exceeded = true;
>> 
>> I am confused. We have noted that we did more than `ShenandoahNoProgressThreshold` collections at this point. So we will fail the allocation request, set `gc_overhead_limit_was_exceeded`, and return `null` to the requester.
>> 
>> What happens at the caller, in response to this set of conditions?
>> 
>> Why then does it make sense to `notify_gc_progress()`, which clears the counter of `_gc_no_progress_count`? Where was the ostensible progress in this case?
>
> Ultimately, the caller will have an OOME raised. The `_gc_no_progress_count` is cleared to allow subsequent mutator allocations to resume the slower block-and-retry loop in `ShenandoahHeap::allocate_memory`.

OK, thanks, that makes sense. Can you add a comment line to that effect?

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

PR Review Comment: https://git.openjdk.org/jdk/pull/15852#discussion_r1334903081