PVE_PER_PVPAGE
#define PVE_LOWAT (PVE_PER_PVPAGE / 2) /* free pv_entry low water mark */
#define PVE_HIWAT (PVE_LOWAT + (PVE_PER_PVPAGE * 2))
struct pv_entry pvents[PVE_PER_PVPAGE];