RFR: 8245022: ParallelGC abuses StarTask to also include partial objarray scan tasks

[Kim Barrett]

> On May 20, 2020, at 4:11 AM, stefan.johansson at oracle.com wrote:
> 
> Hi Kim,
> 
> On 2020-05-20 00:41, Kim Barrett wrote:
>> Please review this change to ParallelGC to also use the recently added
>> ScannerTask (JDK-8244684), eliminating some casts between oop and oop*
>> and use of some misaligned oop* values.
>> Also renamed G1's ScannerTasksQueue[Set] to G1ScannerTasksQueue[Set].
>> I should have used those names in JDK-8244684.  This is consistent
>> with the new PSScannerTasksQueue[Set] now being used by ParallelGC.
>> The types used by G1 and Parallel are currently the same, but don't
>> need to be.
>> Also made a small simplification, reordering the template parameters
>> for PSPromotionManager::copy_and_push_safe_barrier.  By making the
>> promote_immediately flag first and the reference type second we can
>> explicitly specify the non-deduced flag and allow the reference type
>> to be deduced, rather than having to specify both explicitly in calls.
> Nice!
>> CR:
>> https://bugs.openjdk.java.net/browse/JDK-8245022
>> Webrev:
>> https://cr.openjdk.java.net/~kbarrett/8245022/open.00/
> Looks good, one very small nit is the extra spaces left here:
> share/gc/parallel/psPromotionManager.hpp
> ---
> 114  protected:
> 115   static PSScannerTasksQueueSet* stack_array_depth()   { return _stack_array_depth; }
> 
> They were pre-existing, but since we are touching that row, we can remove those spaces that seems to be left from some old alignment.
> ---
> 
> Thanks,
> Stefan

Done.  I also took the opportunity to remove that unnecessary “protected:”, since
PSPromotionManager is not used as a base class.

For the record, new webrevs:
full: https://cr.openjdk.java.net/~kbarrett/8245022/open.01/
incr: https://cr.openjdk.java.net/~kbarrett/8245022/open.01.inc/

The incremental change:

diff -r 72e792be5cf3 -r 2c299a64bed8 src/hotspot/share/gc/parallel/psPromotionManager.hpp
--- a/src/hotspot/share/gc/parallel/psPromotionManager.hpp      Mon May 18 21:37:38 2020 -0400
+++ b/src/hotspot/share/gc/parallel/psPromotionManager.hpp      Wed May 20 08:42:25 2020 -0400
@@ -111,8 +111,8 @@
                                     uint age, bool tenured,
                                     const PSPromotionLAB* lab);
 
- protected:
-  static PSScannerTasksQueueSet* stack_array_depth()   { return _stack_array_depth; }
+  static PSScannerTasksQueueSet* stack_array_depth() { return _stack_array_depth; }
+
  public:
   // Static
   static void initialize();