RFR: 8335480: Only deoptimize threads if needed when closing shared arena [v2]

[Jorn Vernee]

On Mon, 15 Jul 2024 08:41:38 GMT, Doug Simon <dnsimon at openjdk.org> wrote:

>> Jorn Vernee has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   track has_scoped_access for compiled methods
>
> src/hotspot/share/jvmci/jvmciRuntime.cpp line 2186:
> 
>> 2184:         nm->set_has_wide_vectors(has_wide_vector);
>> 2185:         nm->set_has_monitors(has_monitors);
>> 2186:         nm->set_has_scoped_access(true); // conservative
> 
> What does "conservative" imply here? That is, what performance penalty will be incurred for Graal compiled code until it completely supports this "scoped access" bit?

It means we will always deoptimize a top-most frame of any thread, when closing a shared arena, and it is compiled by Graal. (This is a one-off deoptimization though. The compiled code is not thrown away). It essentially matches the current behavior before this PR.

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PR Review Comment: https://git.openjdk.org/jdk/pull/20158#discussion_r1677613801