linux 进程内存占用高分析

通过free命令可以查看系统内存使用情况：

free -m
              total        used        free      shared  buff/cache   available
Mem:           7983        2427        5155          26         400        5272
Swap:          8191          21        8170

buff/cache为缓存部分，在统计memory占用情况时，需要注意这一个值。通过以下命令可以释放缓存：

Writing to this will cause the kernel to drop clean caches, dentries and inodes from memory, causing that memory to become free.
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
As this is a non-destructive operation, and dirty objects are notfreeable, the user should run "sync" first in order to make sure allcached objects are freed.
This tunable was added in 2.6.16.

上面方法需要用户具有root权限，如果不是root，但有sudo权限，可以通过sysctl命令进行设置：

$sync
$sudo sysctl -w vm.drop_caches=3
$sudo sysctl -w vm.drop_caches=0 #恢复默认cache策略

使用这样的cache策略后，进行信用证的压力测试，Linux下该进程的内存占用率不再随时间继续上升。