static int lowmem_adj[6] = {0,1,6,12,
};
static int lowmem_adj_size = 4;
static size_t lowmem_minfree[6] = {3*512, // 6MB2*1024, // 8MB4*1024, // 16MB16*1024, // 64MB
};
static int lowmem_minfree_size = 4;

static int __init lowmem_init(void)
{register_shrinker(&lowmem_shrinker);return 0;
}
static void __exit lowmem_exit(void)
{unregister_shrinker(&lowmem_shrinker);
}
module_init(lowmem_init);
module_exit(lowmem_exit);

static struct shrinker lowmem_shrinker = {.shrink = lowmem_shrink,.seeks = DEFAULT_SEEKS * 16
};

static int lowmem_shrink(int nr_to_scan, gfp_t gfp_mask)
{struct task_struct *p;struct task_struct *selected = NULL;int rem = 0;int tasksize;int i;int min_adj = OOM_ADJUST_MAX + 1;int selected_tasksize = 0;int array_size = ARRAY_SIZE(lowmem_adj);int other_free = global_page_state(NR_FREE_PAGES);int other_file = global_page_state(NR_FILE_PAGES);if(lowmem_adj_size < array_size)array_size = lowmem_adj_size;if(lowmem_minfree_size < array_size)array_size = lowmem_minfree_size;for(i = 0; i < array_size; i++) {if (other_free < lowmem_minfree[i] &&other_file < lowmem_minfree[i]) {min_adj = lowmem_adj[i];break;}}if(nr_to_scan > 0)lowmem_print(3, "lowmem_shrink %d, %x, ofree %d %d, ma %d\n", nr_to_scan, gfp_mask, other_free, other_file, min_adj);rem = global_page_state(NR_ACTIVE_ANON) +global_page_state(NR_ACTIVE_FILE) +global_page_state(NR_INACTIVE_ANON) +global_page_state(NR_INACTIVE_FILE);if (nr_to_scan <= 0 || min_adj == OOM_ADJUST_MAX + 1) {lowmem_print(5, "lowmem_shrink %d, %x, return %d\n", nr_to_scan, gfp_mask, rem);return rem;}read_lock(&tasklist_lock);for_each_process(p) {if (p->oomkilladj < min_adj || !p->mm)continue;tasksize = get_mm_rss(p->mm);if (tasksize <= 0)continue;if (selected) {if (p->oomkilladj < selected->oomkilladj)continue;if (p->oomkilladj == selected->oomkilladj &&tasksize <= selected_tasksize)continue;}selected = p;selected_tasksize = tasksize;lowmem_print(2, "select %d (%s), adj %d, size %d, to kill\n",p->pid, p->comm, p->oomkilladj, tasksize);}if(selected != NULL) {lowmem_print(1, "send sigkill to %d (%s), adj %d, size %d\n",selected->pid, selected->comm,selected->oomkilladj, selected_tasksize);force_sig(SIGKILL, selected);rem -= selected_tasksize;}lowmem_print(4, "lowmem_shrink %d, %x, return %d\n", nr_to_scan, gfp_mask, rem);read_unlock(&tasklist_lock);return rem;
}

enum zone_stat_item {NR_FREE_PAGES,NR_LRU_BASE,NR_INACTIVE_ANON = NR_LRU_BASE,NR_ACTIVE_ANON,NR_INACTIVE_FILE,NR_ACTIVE_FILE,
#ifdef CONFIG_UNEVICTABLE_LRUNR_UNEVICTABLE,NR_MLOCK,
#elseNR_UNEVICTABLE = NR_ACTIVE_FILE, /* 避免编译错误*/NR_MLOCK = NR_ACTIVE_FILE,
#endifNR_ANON_PAGES,        /* 匿名映射页面*/NR_FILE_MAPPED,        /*映射页面*/NR_FILE_PAGES,NR_FILE_DIRTY,NR_WRITEBACK,NR_SLAB_RECLAIMABLE,NR_SLAB_UNRECLAIMABLE,NR_PAGETABLE,NR_UNSTABLE_NFS,NR_BOUNCE,NR_VMSCAN_WRITE,NR_WRITEBACK_TEMP,    /* 使用临时缓冲区*/
#ifdef CONFIG_NUMANUMA_HIT,            /* 在预定节点上分配*/NUMA_MISS,            /* 在非预定节点上分配*/NUMA_FOREIGN,NUMA_INTERLEAVE_HIT,NUMA_LOCAL,            /* 从本地页面分配*/NUMA_OTHER,            /* 从其他节点分配 */
#endifNR_VM_ZONE_STAT_ITEMS };