RFR: 8227745: Enable Escape Analysis for Better Performance in the Presence of JVMTI Agents

[Richard Reingruber]

On Mon, 14 Sep 2020 04:58:47 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> Hi,
>> 
>> this is the continuation of the review of the implementation for:
>> 
>> https://bugs.openjdk.java.net/browse/JDK-8227745
>> https://bugs.openjdk.java.net/browse/JDK-8233915
>> 
>> It allows for JIT optimizations based on escape analysis even if JVMTI agents acquire capabilities to access references
>> to objects that are subject to such optimizations, e.g. scalar replacement. The implementation reverts such
>> optimizations just before access very much as when switching from JIT compiled execution to the interpreter, aka
>> "deoptimization".  Webrev.8 was the last one before before the transition to Git/Github:
>> 
>> http://cr.openjdk.java.net/~rrich/webrevs/8227745/webrev.8/
>> 
>> Thanks, Richard.
>
> src/hotspot/share/compiler/compileBroker.cpp line 844:
> 
>> 842: void DeoptimizeObjectsALotThread::deoptimize_objects_alot_loop_single() {
>> 843:   HandleMark hm(this);
>> 844:   while (!this->is_terminated()) {
> 
> The terminated state of a thread is used to communicate to other threads whether this thread has terminated. It isn't
> something that can be used to control the work-loop of the thread itself! This is an infinite loop as far as I can see.

You're right. Thanks. I'll make it an explicit infinite loop. This should be ok because DeoptimizeObjectsALotThread's
as the other threads created in CompileBroker::make_thread() are daemon threads.

> src/hotspot/share/compiler/compileBroker.cpp line 862:
> 
>> 860: void DeoptimizeObjectsALotThread::deoptimize_objects_alot_loop_all() {
>> 861:   HandleMark hm(this);
>> 862:   while (!is_terminated()) {
> 
> Same comment as above.

Same reply :)

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PR: https://git.openjdk.java.net/jdk/pull/119