Linux释放内存分析

理论分析：

/proc/sys/vm/drop_caches文件的值用于控制内存，其值可以是0-3之间的数字（Linux系统默认该值为0），代表不同的含义：
0：不释放（系统默认值）
1：释放页缓存
2：释放dentries和inodes
3：释放所有缓存

释放内存执行：echo 1 > /proc/sys/vm/drop_caches
释放完内存后改回去让系统重新自动分配内存：echo 0 >/proc/sys/vm/drop_caches

释放所有缓存，执行：echo 3 > /proc/sys/vm/drop_caches

案例：

[[email protected] ~]# free
             total       used       free     shared    buffers     cached
Mem:       1020276     568484     451792          0       2580      35964
-/+ buffers/cache:     529940     490336
Swap:            0          0          0
[[email protected] ~]# free -m
             total       used       free     shared    buffers     cached
Mem:           996        725        271          0         69        126
-/+ buffers/cache:        528        467
Swap:            0          0          0
[[email protected] ~]# echo 3 > /proc/sys/vm/drop_caches
[[email protected] ~]# free -m
             total       used       free     shared    buffers     cached
Mem:           996        551        444          0          9         29
-/+ buffers/cache:        513        482
Swap:            0          0          0
[[email protected] ~]# echo 0 > /proc/sys/vm/drop_caches
[[email protected] ~]# free -m
             total       used       free     shared    buffers     cached
Mem:           996        569        427          0         26         29
-/+ buffers/cache:        513        482
Swap:            0          0          0
[[email protected] ~]#