写在前面
- 一个群里看到有小伙伴问，之前也有遇到过。
- 给了参考意见之后感觉好像不是特别对，有点误人子弟:(。
- 所以总结下，博文内容涉及
- Linux内存
查看监控 缓存清理及参数介绍- 一个
定时清理的脚本
- Linux内存
归根结底，长得好，无论男女，怎么都是对的，长得不好看，大概就是万般皆罪。——烽火戏诸侯《剑来》
嗯，关于缓存清理，小伙伴一定不陌生，个人觉得通过修改drop_caches内核参数的形式来清理缓存，只能是在生产环境用于临时解决问题，本质还是要对应用进行分析，看看是什么原因导致的内存溢出等OOM问题，一般情况下，内存溢出可以通过交换分区来确定
当然，如果是因为业务量的原因，业务高峰，或者需要算力等正常原因，可以定期通过sync将缓存区没有写入数据写入磁盘，然后修改内核参数 drop_caches的值来清理缓存，或者通过新建交换分区调整swappiness交换分区频率来解决问题,如果虚机的话可以申请扩内存
系统内存查看
系统内存查看 |
|---|
其中：
Mem：实际的内存 |Swap: 交换分区 |
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buff/Cache缓存的内存大小available可用内存
系统内存监控
系统内存监控 |
|---|
代码语言：javascript复制
vmstat: 是一个内存监控工具,后面的数字为刷新频率 |top不多说
空闲的物理内存的大小。修改drop_caches内核参数清理缓存
我们先看看帮助文档：内核参数的帮助文档查看方式
代码语言：javascript复制┌──[root@liruilongs.github.io]-[/proc/sys/vm]
└─$ man -K drop_caches
--Man-- next: proc(5) [ view (return) | skip (Ctrl-D) | quit (Ctrl-C) ]
嗯，英文好的小伙伴可以看看
代码语言：javascript复制drop_caches
Writing to this will cause the kernel to drop clean caches, as well as
reclaimable slab objects like dentries and inodes. Once dropped, their
memory becomes free.
To free pagecache:
echo 1 > /proc/sys/vm/drop_caches
To free reclaimable slab objects (includes dentries and inodes):
echo 2 > /proc/sys/vm/drop_caches
To free slab objects and pagecache:
echo 3 > /proc/sys/vm/drop_caches
This is a non-destructive operation and will not free any dirty objects.
To increase the number of objects freed by this operation, the user may run
`sync' prior to writing to /proc/sys/vm/drop_caches. This will minimize the
number of dirty objects on the system and create more candidates to be
dropped.
This file is not a means to control the growth of the various kernel caches
(inodes, dentries, pagecache, etc...) These objects are automatically
reclaimed by the kernel when memory is needed elsewhere on the system.
Use of this file can cause performance problems. Since it discards cached
objects, it may cost a significant amount of I/O and CPU to recreate the
dropped objects, especially if they were under heavy use. Because of this,
use outside of a testing or debugging environment is not recommended.
You may see informational messages in your kernel log when this file is
used:
cat (1234): drop_caches: 3
These are informational only. They do not mean that anything is wrong
with your system. To disable them, echo 4 (bit 2) into drop_caches.
手动执行sync命令（描述：sync 命令运行 sync 子例程。如果必须停止系统，则运行sync 命令以确保文件系统的完整性。sync 命令将所有未写的系统缓冲区写到磁盘中，包含已修改的 i-node、已延迟的块 I/O 和读写映射文件）
代码语言：javascript复制┌──(root
