MEMCG_NR_GENS
unsigned long nr_memcgs[MEMCG_NR_GENS];
struct hlist_nulls_head fifo[MEMCG_NR_GENS][MEMCG_NR_BINS];
#define get_memcg_gen(seq) ((seq) % MEMCG_NR_GENS)
for (i = 0; i < MEMCG_NR_GENS; i++) {