RFR: Disable ShHeapUncommit on too-large large-pages

[Aleksey Shipilev]

On 09/11/2018 09:29 AM, Roman Kennke wrote:
>> Yes, like that. Does it still pass tier3 with uber-large pages?
> 
> No. Of course this is a mistake:
> 
> diff -r 03c6138dd68c
> src/hotspot/share/gc/shenandoah/shenandoahHeapRegion.cpp
> --- a/src/hotspot/share/gc/shenandoah/shenandoahHeapRegion.cpp  Tue Sep
> 11 03:15:46 2018 -0400
> +++ b/src/hotspot/share/gc/shenandoah/shenandoahHeapRegion.cpp  Tue Sep
> 11 03:29:01 2018 -0400
> @@ -618,7 +618,7 @@
>    // Otherwise, uncommitting one region may falsely uncommit the adjacent
>    // regions too.
>    // Also see shenandoahArguments.cpp, where it handles UseLargePages.
> -  if (ShenandoahUncommit) {
> +  if (UseLargePages && ShenandoahUncommit) {
>      region_size = MAX2(region_size, os::large_page_size());
>    }
> 
> Ok?

Right. That makes more sense.

-Aleksey