UMA_SMALLEST_UNIT
#define MINALLOCSIZE UMA_SMALLEST_UNIT
rsize = MAX(keg->uk_size, UMA_SMALLEST_UNIT);
_Static_assert(UMA_SMALLEST_UNIT % KASAN_SHADOW_SCALE == 0,
#define SLAB_MAX_SETSIZE (PAGE_SIZE / UMA_SMALLEST_UNIT)