echo 3 > /proc/sys/vm/drop_caches 清理系統緩存

清理系統緩存
當服務器內存使用率高達90%以上時，且有較大耗內存操作時，可以考慮把系統的垃圾內存清理掉。方法如下
linux23:~ # echo 3 > /proc/sys/vm/drop_caches 
linux23:~ # free -m
             total       used       free     shared    buffers     cached
Mem:         32224      32137         86          0         64      27310
-/+ buffers/cache:       4762      27462
Swap:        34815       1506      33309
linux23:~ # echo 3 > /proc/sys/vm/drop_caches
linux23:~ # free -m
             total       used       free     shared    buffers     cached
Mem:         32224      14698      17526          0          3       9927
-/+ buffers/cache:       4768      27456
Swap:        34815       1506      33309