使用cgroups来控制内存使用-白红宇

首先学习网上例子，进行体验性的试验：

首先不限制内存使用来进行下载：

[root@cent6 Desktop]# free -m             total       used       free     shared    buffers     cachedMem:          2006        484       1522          0         29        175-/+ buffers/cache:        279       1727Swap:         4031          0       4031[root@cent6 Desktop]#

然后，再下载约700M:

wget

然后看内存使用情况：

[root@cent6 Desktop]# free -m             total       used       free     shared    buffers     cachedMem:          2006       1224        782          0         33        878-/+ buffers/cache:        312       1694Swap:         4031          0       4031[root@cent6 Desktop]#

确实是用掉了700多M内存。

然后，重新启动，限制内存使用：

[root@cent6 Desktop]# service cgconfig statusStopped#mount -t cgroup -o memory memcg /cgroup # mkdir /cgroup/GroupA  # echo 10M > /cgroup/GroupA/memory.limit_in_bytes  # echo $$ > /cgroup/GroupA/tasks

然后，再看内存状况：

[root@cent6 Desktop]# free -m             total       used       free     shared    buffers     cachedMem:          2006        481       1525          0         29        174-/+ buffers/cache:        276       1729Swap:         4031          0       4031[root@cent6 Desktop]#

再下载约700M:

wget

再看内存使用前后对比:

[root@cent6 Desktop]# free -m             total       used       free     shared    buffers     cachedMem:          2006        512       1494          0         32        186-/+ buffers/cache:        293       1713Swap:         4031          0       4031[root@cent6 Desktop]#

可以知道，大约的内存使用量为 1525-1494=31M。不过free命令观察到的结果是有误差的，程序执行时间长，free就是一个不断累减的值，由于当前shell被限制使用内存最大10M，那么基数很小的情况下，时间越长，误差越大。

下面，看看对PostgreSQL能否产生良好的限制：

再此之前，通过系统设定来看看对postgres用户进行wget操作时的内存的控制：

[postgres@cent6 Desktop]$ cat /etc/cgconfig.conf##  Copyright IBM Corporation. 2007##  Authors:    Balbir Singh 
     
      #  This program is free software; you can redistribute it and/or modify it#  under the terms of version 2.1 of the GNU Lesser General Public License#  as published by the Free Software Foundation.##  This program is distributed in the hope that it would be useful, but#  WITHOUT ANY WARRANTY; without even the implied warranty of#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.## See man cgconfig.conf for further details.## By default, mount all controllers to /cgroup/
      
       mount {    cpuset    = /cgroup/cpuset;    cpu    = /cgroup/cpu;    cpuacct    = /cgroup/cpuacct;    memory    = /cgroup/memory;    devices    = /cgroup/devices;    freezer    = /cgroup/freezer;    net_cls    = /cgroup/net_cls;    blkio    = /cgroup/blkio;}group test1 {    perm {          task{              uid=postgres;              gid=postgres;          }                    admin{             uid=root;             gid=root;           }    } memory {       memory.limit_in_bytes=30M;    }}[postgres@cent6 Desktop]$

还有一个文件，cgrules.conf，也很重要:

[postgres@cent6 Desktop]$ cat /etc/cgrules.conf# /etc/cgrules.conf##Each line describes a rule for a user in the forms:##
                 
              
       
        #
        
         :
             
           
           
            ##Where:# 
            
              can be:# - an user name# - a group name, with @group syntax# - the wildcard *, for any user or group.# - The %, which is equivalent to "ditto". This is useful for# multiline rules where different cgroups need to be specified# for various hierarchies for a single user.## 
             
               is optional and it can be:# - a process name# - a full command path of a process## 
              
                can be:# - comma separated controller names (no spaces)# - * (for all mounted controllers)## 
               
                 can be:# - path with-in the controller hierarchy (ex. pgrp1/gid1/uid1)## Note:# - It currently has rules based on uids, gids and process name.## - Don't put overlapping rules. First rule which matches the criteria# will be executed.## - Multiline rules can be specified for specifying different cgroups# for multiple hierarchies. In the example below, user "peter" has# specified 2 line rule. First line says put peter's task in test1/# dir for "cpu" controller and second line says put peter's tasks in# test2/ dir for memory controller. Make a note of "%" sign in second line.# This is an indication that it is continuation of previous rule.###
                 
                  
                  
                   ##john cpu usergroup/faculty/john/#john:cp cpu usergroup/faculty/john/cp#@student cpu,memory usergroup/student/#peter cpu test1/#% memory test2/#@root * admingroup/#* * default/# End of file postgres memory test1/#[postgres@cent6 Desktop]$

在root用户，设置如下两个服务随系统启动：

chkconfig cgconfig on

chkconfig cgred on

然后重新启动系统后，用postgres用户进行登录，进行检验：

[postgres@cent6 Desktop]$ free -m             total       used       free     shared    buffers     cachedMem:          2006        381       1625          0         25        134-/+ buffers/cache:        221       1785

[postgres@cent6 Desktop]$ wget http://centos.arcticnetwork.ca/6.4/isos/x86_64/CentOS-6.4-x86_64-LiveCD.iso

执行完毕后，看内存状况，成功。

[postgres@cent6 Desktop]$ free -m             total       used       free     shared    buffers     cachedMem:          2006        393       1613          0         28        141-/+ buffers/cache:        224       1782Swap:         4031         67       3964[postgres@cent6 Desktop]$

下面看对postgresql中执行sql 的限制如何：

步骤1: 对/etc/cgconfig.conf 文件和 /etc/cgrules.conf 文件的设置如前所述。

步骤2: 运行前查看内存状况：

[postgres@cent6 Desktop]$ free -m

total used free shared buffers cached

Mem: 2006 384 1622 0 26 138

-/+ buffers/cache: 219 1787

Swap: 4031 87 3944

[postgres@cent6 Desktop]$

步骤3: 开始处理大量数据(约600MB)

postgres=# select count(*) from test01; count -------     0(1 row) postgres=# insert into test01 values(generate_series(1,614400),repeat( chr(int4(random()*26)+65),1024));

运行刚刚开始，就出现了如下的错误：

The connection to the server was lost. Attempting reset: Failed.!>

这和之前碰到的崩溃情形一致。

PostgreSQL的log本身是这样的：

[postgres@cent6 pgsql]$ LOG:  database system was shut down at 2013-09-09 16:20:29 CSTLOG:  database system is ready to accept connectionsLOG:  autovacuum launcher startedLOG:  server process (PID 2697) was terminated by signal 9: KilledDETAIL:  Failed process was running: insert into test01 values(generate_series(1,614400),repeat( chr(int4(random()*26)+65),1024));LOG:  terminating any other active server processesWARNING:  terminating connection because of crash of another server processDETAIL:  The postmaster has commanded this server process to roll back the current transaction and exit, because another server process exited abnormally and possibly corrupted shared memory.HINT:  In a moment you should be able to reconnect to the database and repeat your command.FATAL:  the database system is in recovery modeLOG:  all server processes terminated; reinitializingLOG:  database system was interrupted; last known up at 2013-09-09 17:35:42 CSTLOG:  database system was not properly shut down; automatic recovery in progressLOG:  redo starts at 1/9E807C90LOG:  unexpected pageaddr 1/946BE000 in log file 1, segment 159, offset 7069696LOG:  redo done at 1/9F6BDB50LOG:  database system is ready to accept connectionsLOG:  autovacuum launcher started

通过dmesg命令，可以看到，发生了Out of Memory错误，这次是 cgroup out of memory

[postgres@cent6 Desktop]$ dmesg | grep post[ 2673]   500  2673    64453      200   0       0             0 postgres[ 2675]   500  2675    64494       79   0       0             0 postgres[ 2676]   500  2676    64453       75   0       0             0 postgres[ 2677]   500  2677    64453       77   0       0             0 postgres[ 2678]   500  2678    64667       80   0       0             0 postgres[ 2679]   500  2679    28359       72   0       0             0 postgres[ 2697]   500  2697    64764      100   0       0             0 postgres[ 2673]   500  2673    64453      200   0       0             0 postgres[ 2675]   500  2675    64494       79   0       0             0 postgres[ 2676]   500  2676    64453       75   0       0             0 postgres[ 2677]   500  2677    64453       77   0       0             0 postgres[ 2678]   500  2678    64667       80   0       0             0 postgres[ 2679]   500  2679    28359       72   0       0             0 postgres[ 2697]   500  2697    64764      100   0       0             0 postgres[ 2673]   500  2673    64453      208   0       0             0 postgres[ 2675]   500  2675    64494       79   0       0             0 postgres[ 2676]   500  2676    64453       98   0       0             0 postgres[ 2677]   500  2677    64453      782   0       0             0 postgres[ 2678]   500  2678    64667      133   0       0             0 postgres[ 2679]   500  2679    28359       86   0       0             0 postgres[ 2697]   500  2697    73075     3036   0       0             0 postgresMemory cgroup out of memory: Kill process 2697 (postgres) score 1000 or sacrifice childKilled process 2697, UID 500, (postgres) total-vm:292300kB, anon-rss:8432kB, file-rss:3712kB[postgres@cent6 Desktop]$

我怀疑自己的内存开得过小了，影响到一些基本的运行。PostgreSQL本身也需要一些资源(shared_buffers、wal_buffers都需要用一些内存)

所以我调整了参数 memory.limit_in_bytes=300M ，再次运行：

前述的sql问处理1200MB数据，成功结束，内存没有过多增长。

本文转自健哥的数据花园博客园博客，原文链接：http://www.cnblogs.com/gaojian/p/3305551.html，如需转载请自行联系原作者