MEM_CGROUP_ID_SHIFT
#define MEM_CGROUP_ID_MAX ((1UL << MEM_CGROUP_ID_SHIFT) - 1)
MEM_CGROUP_ID_SHIFT)
eviction = (eviction << MEM_CGROUP_ID_SHIFT) | memcgid;
memcgid = entry & ((1UL << MEM_CGROUP_ID_SHIFT) - 1);
entry >>= MEM_CGROUP_ID_SHIFT;