RFR (XS) 8242211: Shenandoah: remove ShenandoahHeuristics::RegionData::_seqnum_last_alloc

[Roman Kennke]

Right. Do it!

Thanks,
Roman

> RFE:
>   https://bugs.openjdk.java.net/browse/JDK-8242211
> 
> This field is not needed anymore after Traversal removal, and it only wastes native memory and time
> spent working through region data.
> 
> Fix:
> 
> diff -r 4d759a99c277 src/hotspot/share/gc/shenandoah/shenandoahHeuristics.cpp
> --- a/src/hotspot/share/gc/shenandoah/shenandoahHeuristics.cpp  Mon Apr 06 10:31:07 2020 +0200
> +++ b/src/hotspot/share/gc/shenandoah/shenandoahHeuristics.cpp  Mon Apr 06 14:43:55 2020 +0200
> @@ -43,24 +43,4 @@
>  }
> 
> -int ShenandoahHeuristics::compare_by_garbage_then_alloc_seq_ascending(RegionData a, RegionData b) {
> -  int r = compare_by_garbage(a, b);
> -  if (r != 0) {
> -    return r;
> -  }
> -  return compare_by_alloc_seq_ascending(a, b);
> -}
> -
> -int ShenandoahHeuristics::compare_by_alloc_seq_ascending(RegionData a, RegionData b) {
> -  if (a._seqnum_last_alloc == b._seqnum_last_alloc)
> -    return 0;
> -  else if (a._seqnum_last_alloc < b._seqnum_last_alloc)
> -    return -1;
> -  else return 1;
> -}
> -
> -int ShenandoahHeuristics::compare_by_alloc_seq_descending(RegionData a, RegionData b) {
> -  return -compare_by_alloc_seq_ascending(a, b);
> -}
> -
>  ShenandoahHeuristics::ShenandoahHeuristics() :
>    _region_data(NULL),
> diff -r 4d759a99c277 src/hotspot/share/gc/shenandoah/shenandoahHeuristics.hpp
> --- a/src/hotspot/share/gc/shenandoah/shenandoahHeuristics.hpp  Mon Apr 06 10:31:07 2020 +0200
> +++ b/src/hotspot/share/gc/shenandoah/shenandoahHeuristics.hpp  Mon Apr 06 14:43:55 2020 +0200
> @@ -76,5 +76,4 @@
>      ShenandoahHeapRegion* _region;
>      size_t _garbage;
> -    uint64_t _seqnum_last_alloc;
>    } RegionData;
> 
> @@ -98,7 +97,4 @@
> 
>    static int compare_by_garbage(RegionData a, RegionData b);
> -  static int compare_by_garbage_then_alloc_seq_ascending(RegionData a, RegionData b);
> -  static int compare_by_alloc_seq_ascending(RegionData a, RegionData b);
> -  static int compare_by_alloc_seq_descending(RegionData a, RegionData b);
> 
>    RegionData* get_region_data_cache(size_t num);
> 
> Testing: hotspot_gc_shenandoah {fastdebug,release}
>