RFR: Convert magic value to ShenandoahPacingSurcharge

[Roman Kennke]

Am 14.08.2018 um 10:48 schrieb Aleksey Shipilev:
> The change speaks for itself:
> 
> diff -r b3dae83fdf52 src/hotspot/share/gc/shenandoah/shenandoahPacer.cpp
> --- a/src/hotspot/share/gc/shenandoah/shenandoahPacer.cpp       Tue Aug 14 09:53:21 2018 +0200
> +++ b/src/hotspot/share/gc/shenandoah/shenandoahPacer.cpp       Tue Aug 14 10:47:33 2018 +0200
> @@ -69,3 +69,3 @@
>    tax *= 3;                          // mark is phase 1 of 3, claim 1/3 of free for it
> -  tax *= 1.1;                        // additional surcharge to help unclutter heap
> +  tax *= ShenandoahPacingSurcharge;  // additional surcharge to help unclutter heap
> 
> @@ -98,3 +98,3 @@
>    tax = MAX2<double>(1, tax);        // never allocate more than GC processes during the phase
> -  tax *= 1.1;                        // additional surcharge to help unclutter heap
> +  tax *= ShenandoahPacingSurcharge;  // additional surcharge to help unclutter heap
> 
> @@ -119,3 +119,3 @@
>    tax = MAX2<double>(1, tax);        // never allocate more than GC processes during the phase
> -  tax *= 1.1;                        // additional surcharge to help unclutter heap
> +  tax *= ShenandoahPacingSurcharge;  // additional surcharge to help unclutter heap
> 
> @@ -143,3 +143,3 @@
>    double tax = 1.0 * live / taxable; // base tax for available free space
> -  tax *= 1.1;                        // additional surcharge to help unclutter heap
> +  tax *= ShenandoahPacingSurcharge;  // additional surcharge to help unclutter heap
> 
> @@ -168,3 +168,3 @@
>    tax = MAX2<double>(1, tax);              // never allocate more than GC collects during the cycle
> -  tax *= 1.1;                              // additional surcharge to help unclutter heap
> +  tax *= ShenandoahPacingSurcharge;        // additional surcharge to help unclutter heap
> 
> diff -r b3dae83fdf52 src/hotspot/share/gc/shenandoah/shenandoah_globals.hpp
> --- a/src/hotspot/share/gc/shenandoah/shenandoah_globals.hpp    Tue Aug 14 09:53:21 2018 +0200
> +++ b/src/hotspot/share/gc/shenandoah/shenandoah_globals.hpp    Tue Aug 14 10:47:33 2018 +0200
> @@ -406,2 +406,9 @@
>                                                                              \
> +  experimental(double, ShenandoahPacingSurcharge, 1.1,                      \
> +          "Additional pacing tax surcharge to help unclutter the heap. "    \
> +          "Larger values makes the pacing more aggressive. Lower values "   \
> +          "risk GC cycles finish with less memory than were available at "  \
> +          "the beginning of it.")                                           \
> +          range(1, 100)                                                     \
> +                                                                            \
>    experimental(uintx, ShenandoahCriticalFreeThreshold, 1,                   \
> 
> 
> Testing: tier3_gc_shenandoah
> 
> Thanks,
> -Aleksey
> 

Yup. Go!
Roman