kvm动态调整虚机内存

nagios报警，有一台实机的内存使用率达到极限了，告警信息如下：

MEMORY CRITICAL : Mem used: 99.61%, Swap used: 95.98%  

上帝啊，128G的内存居然被用光了！！！

登上这台机器，验证一下，发现确实啥也不剩了，没有任何缓存，而且连交换分区都用了

# free -g
             total       used       free     shared    buffers     cached
Mem:           125        125          0          0          0          0  
-/+ buffers/cache:        125          0
Swap:            8          7          0  

看看上面跑了什么，居然跑了12台虚机

virsh list --all  
 Id    Name                           State
----------------------------------------------------
 1     vis-16-13-27                   running
 2     vis-16-13-29                   running
 3     vis-16-13-74                   running
 4     vis-16-13-26                   running
 5     vis-16-13-25                   running
 6     vis-16-13-30                   running
 7     vis-16-13-28                   running
 15    vis-16-13-33                   running
 41    vis-16-13-75                   running
 44    vis-16-13-24                   running
 45    vis-16-13-22                   running
 46    vis-16-13-23                   running

检测一下每个虚机的内存使用情况

virsh dominfo vis-16-13-28  
d:             7  
Name:           vis-16-13-28  
UUID:           083bde71-764a-23ad-a593-e81edc7adde1  
OS Type:        hvm  
State:          running  
CPU(s):         4  
CPU time:       2515172.9s  
Max memory:     7864320 KiB  
Used memory:    7864320 KiB  
Persistent:     yes  
Autostart:      enable  
Managed save:   no  
Security model: none  
Security DOI:   0  

居然也都是全满

于是登录到虚机，用free -g查看

[root@vis-16-13-28 ~]# free -m
             total       used       free     shared    buffers     cached
Mem:          7366       7233        132          0        148       3359  
-/+ buffers/cache:       3726       3640
Swap:            0          0          0  

分明是只用了4G，空闲3G

调整一下，给虚机分5G内存

virsh setmem vis-16-13-28 5120m  

再看实体机的内存

free -g  
             total       used       free     shared    buffers     cached
Mem:           125        123          2          0          0          0  
-/+ buffers/cache:        122          3
Swap:            8          7          0  

放出来了3G，警报消除

看虚机的内存

[root@vis-16-13-28 ~]# free -m
             total       used       free     shared    buffers     cached
Mem:          4806       4129        676          0         71        723  
-/+ buffers/cache:       3335       1471
Swap:            0          0          0  

也正常。ok，搞定。