RFR (XS) 8243460: Shenandoah: purge init_update_refs_prepare counter

[Roman Kennke]

Ok.

Roman


> Simple RFE:
>   https://bugs.openjdk.java.net/browse/JDK-8243460
> 
> After JDK-8243291, init_update_refs_prepare counter is effectively zero on most paths and does not
> carry its weight. Removing it unclutters the logs.
> 
> Fix:
> 
> diff -r 4103af83d98e src/hotspot/share/gc/shenandoah/shenandoahHeap.cpp
> --- a/src/hotspot/share/gc/shenandoah/shenandoahHeap.cpp        Thu Apr 23 12:14:58 2020 +0900
> +++ b/src/hotspot/share/gc/shenandoah/shenandoahHeap.cpp        Thu Apr 23 07:50:01 2020 +0200
> @@ -2507,8 +2507,5 @@
>    set_update_refs_in_progress(true);
> 
> -  {
> -    ShenandoahGCSubPhase phase(ShenandoahPhaseTimings::init_update_refs_prepare);
> -    _update_refs_iterator.reset();
> -  }
> +  _update_refs_iterator.reset();
> 
>    if (ShenandoahPacing) {
> diff -r 4103af83d98e src/hotspot/share/gc/shenandoah/shenandoahPhaseTimings.hpp
> --- a/src/hotspot/share/gc/shenandoah/shenandoahPhaseTimings.hpp        Thu Apr 23 12:14:58 2020 +0900
> +++ b/src/hotspot/share/gc/shenandoah/shenandoahPhaseTimings.hpp        Thu Apr 23 07:50:01 2020 +0200
> @@ -91,5 +91,4 @@
>    f(init_update_refs,                               "Pause Init  Update Refs (N)")     \
>    f(init_update_refs_retire_gclabs,                 "  Retire GCLABs")                 \
> -  f(init_update_refs_prepare,                       "  Prepare")                       \
>                                                                                         \
>    f(final_update_refs_gross,                        "Pause Final Update Refs (G)")     \
>