RFR: Remove 5 develop options from GC code.

[David Lindholm]

Thomas,

Thanks for looking at this.

On 2015-10-15 10:48, Thomas Schatzl wrote:
> Hi David,
>
> On Fri, 2015-10-09 at 15:47 +0200, David Lindholm wrote:
>> Hi,
>>
>> Please review this patch that removes the following 5 develop options
>> from the GC code:
>>
>> ScavengeWithObjectsInToSpace
>> ParallelOldGCSplitALot
>> ParallelOldGCSplitInterval
>> PSAdjustTenuredGenForMinorPause
>> PSAdjustYoungGenForMajorPause
>>
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8139277   which is a
>> subtask to
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8139276
>> Webrev: http://cr.openjdk.java.net/~david/JDK-8139277/webrev.00/
>>
>> Testing: Passed JPRT
>>
>   - psAdaptiveSizePolicy.cpp:532: the change removes the if-clause
> completely, potentially changing behavior. I would prefer if that were
> not the case, as I cannot immediately see that there is no difference
> here.

I know, I choose between doing this or just leave an empty block (which 
would not change behaviour). If you want I can do the empty block instead.

>   - not sure how the change in psScavenge.cpp:300, 351, 680, theremoval
> of code triggered by ZapUnusedArea is related to this change. Unless I
> overlooked something, it seems to be something interesting to keep.

Since ScavengeWithObjectsInToSpace will always be false now (the default 
value of the flag when it existed), we will never take the old "else if" 
branch on line 351, so the value of ZapUnusedHeapArea will not matter 
any more here. All mangling will be done by 
young_gen->to_space()->clear(SpaceDecorator::Mangle); on line 344. Since 
the whole space will be mangled always now (if ZapUnusedHeapArea is 
true), I assumed that we did not need the block on line 300. The calls 
on lines 681-683 seems to be debugcode under #ifdef DEBUG_MANGLING, and 
besides it is also called at the end of 
SpaceMangler::mangle_unused_area(). And mangling is not asynchronous, as 
one can me led to believe by the name of that function, 
check_mangled_unused_area_complete().


Thanks,
David


> Thanks,
>    Thomas
>
>