ipcs和ipcrm管理共享内存、消息队列、信号 /proc/sys/vm/drop_caches管理缓存

2015-07-25 10:13:00
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原创 1334
摘要:ipcs和ipcrm管理共享内存、消息队列、信号 /proc/sys/vm/drop_caches管理缓存

一、ipcs命令(显示进程间通信信息)

ipcs - provide information on ipc facilities

-m     shared memory segments

-q     message queues

-s     semaphore arrays

-a     all (this is the default)


显示共享内存信息

[root@ebs-19233 ~]# ipcs -m
------ Shared Memory Segments --------
key        shmid      owner      perms      bytes      nattch     status      
0x00000000 1638400    root       600        524288     16         dest


二、ipcrm命令(删除进程间通信信息

ipcrm [ -M key | -m id | -Q key | -q id | -S key | -s id ] ...

-m shmid:removes the shared memory segment identified by shmid after the last detach is performed.

-q msgid:removes the message queue identified by msgid.

-s semid:removes the semaphore identified by semid.


[root@ebs-19233 ~]# ipcs -m
------ Shared Memory Segments --------
key        shmid      owner      perms      bytes      nattch     status      
0x00000000 1638400    root       600        524288     16         dest         
0x28a11375 1671169    root       644        1000       0                       
[root@ebs-19233 ~]# ipcrm -m 1671169
[root@ebs-19233 ~]# ipcs -m
------ Shared Memory Segments --------
key        shmid      owner      perms      bytes      nattch     status      
0x00000000 1638400    root       600        524288     16         dest


三、/proc/sys/vm/drop_caches管理缓存

操作系统可用内存:free memory

应用进程可用内存:free memory+buffers+cached(buffers和cached可以被很快回收)

buffers:磁盘io写缓存

cached:频繁访问的文件缓存,如果值很大说明缓存的文件内容很多。


To free pagecache, use echo 1 > /proc/sys/vm/drop_caches;
To free dentries and inodes, use echo 2 > /proc/sys/vm/drop_caches;
to free pagecache, dentries and inodes, use echo 3 > /proc/sys/vm/drop_caches.

Because this is a non-destructive operation and dirty objects are not freeable, the user should run sync first.

#sync //同步到磁盘
#echo 3 >/proc/sys/vm/drop_caches //刷新缓存

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