RFR: Set ShenandoahMinFreeThreshold default to 10%

[Roman Kennke]

Am 03.05.2018 um 11:09 schrieb Aleksey Shipilev:
> Our adopters report again that the default adaptive threshold of 3% is uncomfortably low to avoid
> problems under allocation spikes. We have recommended at least two adopters to set it to 10%, and it
> seems work for them fine.
> 
> Let's make that the real default:
> 
> diff -r 20f6d65431ec src/hotspot/share/gc/shenandoah/shenandoah_globals.hpp
> --- a/src/hotspot/share/gc/shenandoah/shenandoah_globals.hpp	Wed May 02 21:42:13 2018 +0200
> +++ b/src/hotspot/share/gc/shenandoah/shenandoah_globals.hpp	Thu May 03 11:05:19 2018 +0200
> @@ -167,7 +167,7 @@
>                 "Initial remaining free threshold for adaptive heuristics")  \
>            range(0,100)                                                      \
>                                                                              \
> -  experimental(uintx, ShenandoahMinFreeThreshold, 3,                        \
> +  experimental(uintx, ShenandoahMinFreeThreshold, 10,                       \
>                 "Minimum remaining free threshold for adaptive heuristics")  \
>            range(0,100)                                                      \
>                                                                              \
> 
> In my performance runs, it does not regress performance, unless we are dealing with very tight heaps.
> 
> Testing: hotspot_gc_shenandoah, benchmarks
> 
> Thanks,
> -Aleksey
> 

Seems reasonable. Thanks.

Roman