SYM_MEM_CLUSTER_SHIFT
((((unsigned long)(m)) >> SYM_MEM_CLUSTER_SHIFT) & VTOB_HASH_MASK)
struct sym_m_link h[SYM_MEM_CLUSTER_SHIFT - SYM_MEM_SHIFT + 1];
#define SYM_MEM_CLUSTER_SIZE (1UL << SYM_MEM_CLUSTER_SHIFT)