增加swap空间

因java加压包 耗费大量内存，且频率高，centos 服务器16G内存，完全被cached 占满。

[[email protected] home]# free
             total       used       free     shared    buffers     cached
Mem:      16315436   15693128     622308         64     103564   13778428
-/+ buffers/cache:    1811136   14504300

手动释命令

释放方法有三种（系统默认值是0，释放之后你可以再改回0值）：

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

手动释放后不能解决问题，且操作文件因cache被清，速度慢。

想到增加swap空间

[[email protected] home]# mkswap /home/swapfile 
mkswap: /home/swapfile: warning: don't erase bootbits sectors
        on whole disk. Use -f to force.
Setting up swapspace version 1, size = 33554428 KiB
no label, UUID=ab40acb5-66be-4b4c-b706-cd66629a9b27
[[email protected] home]# swapon /home/swapfile 
[[email protected] home]# vim /etc/fstab 
/home/swapfile  swap    swap    defaults        0 0  ##添加到文件中

[[email protected] home]# mount -a
[[email protected] home]# free
             total       used       free     shared    buffers     cached
Mem:      16315436   15113992    1201444         64     101892   13707604
-/+ buffers/cache:    1304496   15010940
Swap:     41787384      64408   41722976

完成。