linux top 和 free 命令及 buffer和 cache 区别

**cache是高速缓存，用于CPU和内存之间的缓冲 
**buffer是I/O缓存，用于内存和硬盘的缓冲*

　buffer 与cache 的区别 
　　 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.

[root@server ~]# free -m
                    total       used       free     shared    buffers     cached
Mem:           249        163         86          0         10             94
-/+ buffers/cache:         58        191
Swap:          511          0          511

其中:

[root@server ~]# free -m
      total  used  free   shared   buffers    cached
Mem:   249   163   86       0       10         94
-/+ buffers/cache: 58      191
Swap:  511    0    511
其中:
total 内存总数
used 已经使用的内存数
free 空闲的内存数
shared 多个进程共享的内存总额
buffers： Buffer Cache
cached： Page Cache
-buffers/cache 的内存数:used - buffers - cached
+buffers/cache 的内存数:free + buffers + cached
**可用的memory=free memory+buffers+cached**