RFR: 8258255: Move PtrQueue active flag to SATBMarkQueue [v2]

[Kim Barrett]

On Thu, 17 Dec 2020 15:07:44 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

>> Kim Barrett has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   tschatzl review
>
> src/hotspot/share/gc/shared/satbMarkQueue.hpp line 155:
> 
>> 153:   // When active, add obj to queue by calling enqueue_known_active.
>> 154:   void enqueue(SATBMarkQueue& queue, oop obj) {
>> 155:     if (queue.is_active()) enqueue_known_active(queue, obj);
> 
> Maybe something for a different CR and probably pre-existing: `enqueue()` in some contexts is already called with `queue.is_active() == true`. I.e. this check is superfluous sometimes, particularly when called for object arrays.

I was planning to look at that later.  I filed a reminder: https://bugs.openjdk.java.net/browse/JDK-8258607

> src/hotspot/share/gc/shared/satbMarkQueue.hpp line 106:
> 
>> 104:   size_t _process_completed_buffers_threshold;
>> 105:   size_t _buffer_enqueue_threshold;
>> 106:   // SATB is only active during marking.  Enqueuing is not done when inactive.
> 
> I would prefer to avoid the double-negation in the second sentence.

Sure.  Changing it to
  // SATB is only active during marking.  Enqueuing is only done when active.

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PR: https://git.openjdk.java.net/jdk/pull/1820