RFR (XS) 8242213: Shenandoah: remove unused ShenandoahHeuristics::_bytes_in_cset

[Roman Kennke]

Ok, let it go! :-)

Roman


> RFE:
>   https://bugs.openjdk.java.net/browse/JDK-8242213
> 
> That field does not seem to be used for anything, yet we update it on critical path during cset
> selection. We should ditch the field and all "uses" of it. Cursory examination seems to indicate it
> was there since the initial integration.
> 
> Fix:
> 
> diff -r f30c66ecc928 src/hotspot/share/gc/shenandoah/heuristics/shenandoahAdaptiveHeuristics.cpp
> --- a/src/hotspot/share/gc/shenandoah/heuristics/shenandoahAdaptiveHeuristics.cpp       Mon Apr 06
> 14:46:40 2020 +0200
> +++ b/src/hotspot/share/gc/shenandoah/heuristics/shenandoahAdaptiveHeuristics.cpp       Mon Apr 06
> 15:04:29 2020 +0200
> @@ -78,3 +78,2 @@
>    size_t cur_garbage = 0;
> -  _bytes_in_cset = 0;
> 
> @@ -92,3 +91,2 @@
>        cset->add_region(r);
> -      _bytes_in_cset += r->used();
>        cur_cset = new_cset;
> diff -r f30c66ecc928 src/hotspot/share/gc/shenandoah/shenandoahHeuristics.cpp
> --- a/src/hotspot/share/gc/shenandoah/shenandoahHeuristics.cpp  Mon Apr 06 14:46:40 2020 +0200
> +++ b/src/hotspot/share/gc/shenandoah/shenandoahHeuristics.cpp  Mon Apr 06 15:04:29 2020 +0200
> @@ -48,3 +48,2 @@
>    _successful_cycles_in_a_row(0),
> -  _bytes_in_cset(0),
>    _cycle_start(os::elapsedTime()),
> @@ -260,3 +259,3 @@
>  void ShenandoahHeuristics::record_allocation_failure_gc() {
> -  _bytes_in_cset = 0;
> +  // Do nothing.
>  }
> @@ -264,4 +263,2 @@
>  void ShenandoahHeuristics::record_requested_gc() {
> -  _bytes_in_cset = 0;
> -
>    // Assume users call System.gc() when external state changes significantly,
> diff -r f30c66ecc928 src/hotspot/share/gc/shenandoah/shenandoahHeuristics.hpp
> --- a/src/hotspot/share/gc/shenandoah/shenandoahHeuristics.hpp  Mon Apr 06 14:46:40 2020 +0200
> +++ b/src/hotspot/share/gc/shenandoah/shenandoahHeuristics.hpp  Mon Apr 06 15:04:29 2020 +0200
> @@ -84,4 +84,2 @@
> 
> -  size_t _bytes_in_cset;
> -
>    double _cycle_start;
> 
> Testing: hotspot_gc_shenandoah
>