M_RNOWAIT
if ((flags & (M_RNOWAIT|M_WAITOK)) == 0) {
while (slgd->NFreeZones > ZoneRelsThresh && (flags & M_RNOWAIT) == 0) {
while (TAILQ_FIRST(&slgd->FreeOvZones) && (flags & M_RNOWAIT) == 0) {
#define M_INTNOWAIT (M_RNOWAIT | M_NULLOK | \
#define M_SYSNOWAIT (M_RNOWAIT | M_NULLOK | M_USE_RESERVE)
#define M_NOWAIT (M_RNOWAIT | M_NULLOK | M_USE_RESERVE)