free - Display amount of free and used memory in the system.free是用来显示系统内存交换内存使用情况的命令。这里我们分析free的结果。
【命令参数】
[root@xxx xxx]# free -h free: invalid option -- h usage: free [-b|-k|-m|-g] [-l] [-o] [-t] [-s delay] [-c count] [-V] -b,-k,-m,-g show output in bytes, KB, MB, or GB -l show detailed low and high memory statistics -o use old format (no -/+buffers/cache line) -t display total for RAM + swap -s update every [delay] seconds -c update [count] times -V display version information and exit
一般使用free -m显示单位MB大小的使用情况
[root@fantawebn004 nginxlog]# free -m
total used free shared buffers cached
Mem: 3955 3712 242 0 459 2028
-/+ buffers/cache: 1224 2730
Swap: 0 0 0
【结果分析】
第2行Mem: 内存总数是3955M，已经使用3712M，剩余242M ， buffers459M cached2028M
内存总数=已经使用+剩余内存
从系统角度看内存的使用量
第3行-/+ buffers/cache： 已经使用1224M ，剩余2730M
从应用的角度看内存使用量
已经使用内存=应用使用内存+buffers+cached
3721 = 1224 + 459 + 2028
第4行Swap: 交换区
A buffer is something that has yet to be "written" to disk.
A cache is something that has been "read" from the disk and stored for later use.
【参考】
http://www.cnblogs.com/coldplayerest/archive/2010/02/20/1669949.html