转:释放linux的swap内存

https://blog.csdn.net/chenghuikai/article/details/77476830

第一步：先执行sync命令
#sync
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sync命令用于强制被改变的内容立刻写入磁盘，更新超块信息，以防止释放，sync命令则可用来强制将内存缓冲区中的数据立即写入磁盘中。
第二步：(如果仅仅是清理swap的话，这一步可以不执行)

#echo 3 > /proc/sys/vm/drop_caches
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此指令输入立即生效，意在释放所有缓存。
关于drop_caches：
drop_caches的详细文档如下：
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.
**echo 1:释放页面缓存
echo 2:释放目录文件和inodes
echo 3:释放所有缓存(页面缓存，目录文件和inodes)**