RFR (S): [9+8u] Min region size should be 256K to allow small heaps

[Roman Kennke]

Am 03.03.2017 um 13:23 schrieb Aleksey Shipilev:
> Hi,
> 
> Turns out, some JDK tool launchers set -Xms8M. Shenandoah fails cryptically then:
> 
> Error occurred during initialization of VM
> Invalid -XX:ShenandoahMinRegionSize option
> 
> While those tools configs are the actual culprit, we might want to bite the
> bullet and afford those smaller heaps. And turns out, we supposed to! Because
> the failure is due to requesting 10 regions, with SHR::MIN_REGION_SIZE being
> 256K. But that ShenandoahMinRegionSize default is 1M, oops. I suggest we change
> ShenandoahMinRegionSize to match MIN_REGION_SIZE:
>   http://cr.openjdk.java.net/~shade/shenandoah/regionsizes-match/webrev.01/
> 
> I don't want to depend on ShenandoahHeapRegion in *globals.hpp. Tests should
> cover future discrepancies.
> 
> The patch applies to 8u with some fuzz, and I will push it there simultaneously
> with 9.
> 
> Testing: hotspot_gc_shenandoah

Ok!

Roman