RFR: Fix assertion failure of matrix size due to vm allocation granularity on Win x64

[Zhengyu Gu]

This patch fixes assertion failure of TestGCThreadGroups on Windows x64.

   Internal Error 
(c:/Users/zhengyu/workspace/shenandoah-jdk10/src/hotspot/share/memory/virtualspace.cpp:103), 
pid=6404, tid=4448
   assert((size & (granularity - 1)) == 0) failed: size not aligned to 
os::vm_allocation_granularity()

On Windows x64, vm_allocation_granularity is 64K, instead of 4K.


Webrev: file:///home/zgu/webrevs/shenandoah/matrix_size/webrev.00/index.html


I will look into other vm allocations, and fix them separately if find any.

Test:

   hotspot_gc_shenandoah: fastdebug on Linux x64 and Windows x64


Thanks,

-Zhengyu