RFR: 8265489: Stress test times out because of long ObjectSynchronizer::monitors_iterate(...) operation

[Daniel D.Daugherty]

On Fri, 3 Sep 2021 01:26:01 GMT, Daniel D. Daugherty <dcubed at openjdk.org> wrote:

>> monitors_iterate make several checks which often are true before filter monitor by a thread. It might take a lot of time when there are a lot of threads. So it makes sense to first check thread and only then other conditions.
>
> src/hotspot/share/runtime/synchronizer.cpp line 981:
> 
>> 979:     if (mid->owner() != thread) {
>> 980:       return;
>> 981:     }
> 
> The `iter` is processing the in-use-list and you're bailing the iteration
> when you run into an ObjectMonitor that is not owned by `thread`, but
> that doesn't mean that there's not an ObjectMonitor owned by `thread`
> later on in the in-use-list.
> 
> So I could see you doing a `continue` here, but not a `return`.

Thanks for resolving the above comment.

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PR: https://git.openjdk.java.net/jdk/pull/5194