RFR: Conditionalize PerfDataMemorySize on enabled heap sampling

[Christine Flood]

Looks good,

Thanks!

Christine


On Fri, Jan 26, 2018 at 12:00 PM, Aleksey Shipilev <shade at redhat.com> wrote:
> Saves some memory when sampling is not enabled (default case), and boosts up when we deal with lots
> of Shenandoah sampling data:
>
> diff -r 3c12448ec444 src/hotspot/share/runtime/arguments.cpp
> --- a/src/hotspot/share/runtime/arguments.cpp   Thu Jan 25 18:44:13 2018 +0100
> +++ b/src/hotspot/share/runtime/arguments.cpp   Fri Jan 26 17:58:21 2018 +0100
> @@ -2035,8 +2035,10 @@
>      FLAG_SET_DEFAULT(ParallelRefProcEnabled, true);
>    }
>
> -  if (FLAG_IS_DEFAULT(PerfDataMemorySize)) {
> -    FLAG_SET_DEFAULT(PerfDataMemorySize, 512*K);
> +  if (ShenandoahRegionSampling && FLAG_IS_DEFAULT(PerfDataMemorySize)) {
> +    // When sampling is enabled, max out the PerfData memory to get more
> +    // Shenandoah data in, including Matrix.
> +    FLAG_SET_DEFAULT(PerfDataMemorySize, 2048*K);
>    }
>
>  #ifdef COMPILER2
>
> Testing: hotspot_gc_shenandoah
>
> Thanks,
> -Aleksey
>