RFR (XS) 8242267: Shenandoah: regions space needs to be aligned by os::vm_allocation_granularity()

[Aleksey Shipilev]

Bug:
  https://bugs.openjdk.java.net/browse/JDK-8242267

SAP folks report their Windows CI fails Shenandoah tests.

I believe this is the fix:

diff -r 3f8d03880bf5 src/hotspot/share/gc/shenandoah/shenandoahHeap.cpp
--- a/src/hotspot/share/gc/shenandoah/shenandoahHeap.cpp        Tue Apr 07 03:25:11 2020 +0000
+++ b/src/hotspot/share/gc/shenandoah/shenandoahHeap.cpp        Tue Apr 07 11:48:56 2020 +0200
@@ -284,4 +284,5 @@
   size_t region_align = align_up(sizeof(ShenandoahHeapRegion), SHENANDOAH_CACHE_LINE_SIZE);
   size_t region_storage_size = align_up(region_align * _num_regions, region_page_size);
+  region_storage_size = align_up(region_storage_size, os::vm_allocation_granularity());

   ReservedSpace region_storage(region_storage_size, region_page_size);

Testing: Linux x86_64 hotspot_gc_shenandoah + asked SAP folks to confirm

-- 
Thanks,
-Aleksey