Linux下清理内存和Cache方法

暂时目前的环境处理方法比较简单：
在root用户下添加计划任务：

/10 * sync;echo 3 > /proc/sys/vm/drop_caches;

每十分钟执行一次，先将脏数据写回硬盘，以后释放缓存页和入口信息和节点信息等；

Linux下清理内存和Cache方法 /proc/sys/vm/drop_caches

Linux下清理内存和Cache方法 /proc/sys/vm/drop_caches

频繁的文件访问会致使系统的Cache使用量大增

$ free -m
total used free shared buffers cached
Mem: 3955 3926 28 0 55 3459
-/+ buffers/cache: 411 3544
Swap: 5726 0 5726

free内存减小到几十兆，系统运行缓慢

运行sync将dirty的内容写回硬盘
$sync

经过修改proc系统的drop_caches清理free的cache
$echo 3 > /proc/sys/vm/drop_caches

drop_caches的详细文档以下：
Writing to this will cause the kernel to drop clean caches, dentries and inodes from memory, causing that memory to become free.
To free pagecache:

• echo 1 > /proc/sys/vm/drop_caches
  To free dentries and inodes:
• echo 2 > /proc/sys/vm/drop_caches
  To free pagecache, dentries and inodes:
• echo 3 > /proc/sys/vm/drop_caches
  As this is a non-destructive operation, and dirty objects are notfreeable, the user should run "sync" first in order to make sure allcached objects are freed.
  This tunable was added in 2.6.16.

修改/etc/sysctl.conf 添加以下选项后就不会内存持续增长
vm.dirty_ratio = 1
vm.dirty_background_ratio=1
vm.dirty_writeback_centisecs=2
vm.dirty_expire_centisecs=3
vm.drop_caches=3
vm.swappiness =100
vm.vfs_cache_pressure=163
vm.overcommit_memory=2
vm.lowmem_reserve_ratio=32 32 8
kern.maxvnodes=3

上面的设置比较粗暴，使cache的做用基本没法发挥。须要根据机器的情况进行适当的调节寻找最佳的折衷。