WCE_REGION_SIZE
_page_per_region = WCE_REGION_SIZE / _page_size;
{ return ROUND(v, uint32_t(WCE_REGION_SIZE)); }
{ return TRUNC(v, uint32_t(WCE_REGION_SIZE)); }
enum { BLOCK_SIZE = WCE_REGION_SIZE * 64 }; // 4MByte