注意:以下文档只适用于TOP接口,请谨慎使用!
测试环境:CentOS Linux release 7.0.1406 (Core) ,CentOS Linux release 7.2.1511 (Core)
配置:CPU 1核, 内存4G
注:版本不同,变化的大小也有差异;内存越大变化越明显。
修改前配置前内存使用情况如下
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 | <ol class = "linenums" > <li class = "L0" ><span class = "pun" >[</span><span class = "pln" >root @test </span><span class = "pun" >-</span><span class = "lit" > 1 </span><span class = "pln" > </span><span class = "pun" >~]#</span><span class = "pln" > dmesg </span><span class = "pun" >|</span><span class = "pln" > grep </span><span class = "typ" >Memory</span></li> <li class = "L1" ><span class = "pun" >[</span><span class = "pln" > </span><span class = "lit" > 0.000000 </span><span class = "pun" >]</span><span class = "pln" > </span><span class = "typ" >Memory</span><span class = "pun" >:</span><span class = "pln" > </span><span class = "lit" >3865640k</span><span class = "pun" >/</span><span class = "lit" >4456448k</span><span class = "pln" > available </span><span class = "pun" >(</span><span class = "lit" >6108k</span><span class = "pln" > kernel code</span><span class = "pun" >,</span><span class = "pln" > </span><span class = "lit" >262536k</span><span class = "pln" > absent</span><span class = "pun" >,</span><span class = "pln" > </span><span class = "lit" >328272k</span><span class = "pln" > reserved</span><span class = "pun" >,</span><span class = "pln" > </span><span class = "lit" >4071k</span><span class = "pln" > data</span><span class = "pun" >,</span><span class = "pln" > </span><span class = "lit" >1584k</span><span class = "pln" > init</span><span class = "pun" >)</span></li> <li class = "L2" ><span class = "pun" >[</span><span class = "pln" >root @test </span><span class = "pun" >-</span><span class = "lit" > 1 </span><span class = "pln" > </span><span class = "pun" >~]#</span><span class = "pln" > free </span><span class = "pun" >-</span><span class = "pln" >m</span></li> <li class = "L3" ><span class = "pln" > total used free shared buffers cached</span></li> <li class = "L4" ><span class = "typ" >Mem</span><span class = "pun" >:</span><span class = "pln" > </span><span class = "lit" > 3535 </span><span class = "pln" > </span><span class = "lit" > 165 </span><span class = "pln" > </span><span class = "lit" > 3369 </span><span class = "pln" > </span><span class = "lit" > 8 </span><span class = "pln" > </span><span class = "lit" > 11 </span><span class = "pln" > </span><span class = "lit" > 77 </span></li> <li class = "L5" ><span class = "pun" >-</span><span class = "str" >/+ buffers/</span><span class = "pln" >cache</span><span class = "pun" >:</span><span class = "pln" > </span><span class = "lit" > 76 </span><span class = "pln" > </span><span class = "lit" > 3459 </span></li> <li class = "L6" ><span class = "typ" >Swap</span><span class = "pun" >:</span><span class = "pln" > </span><span class = "lit" > 0 </span><span class = "pln" > </span><span class = "lit" > 0 </span><span class = "pln" > </span><span class = "lit" > 0 </span></li> <li class = "L7" ><span class = "pun" >[</span><span class = "pln" >root @test </span><span class = "pun" >-</span><span class = "lit" > 1 </span><span class = "pln" > </span><span class = "pun" >~]#</span><span class = "pln" > </span></li> </ol> |
修改前配置如下
/boot/grub2/grub.cfg的配置情况如下图crashkernel=auto
运行以下命令修改/boot/grub2/grub.cfg配置文件。
1 2 3 4 5 6 7 8 9 | <ol class = "linenums" > <li class = "L0" ><span class = "pln" >sudo cp </span><span class = "pun" >-</span><span class = "pln" >p </span><span class = "pun" >/</span><span class = "pln" >etc</span><span class = "pun" >/</span><span class = "kwd" > default </span><span class = "pun" >/</span><span class = "pln" >grub </span><span class = "pun" >/</span><span class = "pln" >etc</span><span class = "pun" >/</span><span class = "kwd" > default </span><span class = "pun" >/</span><span class = "pln" >grub</span><span class = "pun" >.</span><span class = "pln" >original </span><span class = "com" >#备份grub文件</span></li> <li class = "L1" ><span class = "pln" >sudo sed </span><span class = "pun" >--</span><span class = "kwd" >in</span><span class = "pun" >-</span><span class = "pln" >place </span><span class = "str" > 's/crashkernel=auto /crashkernel=0M /' </span><span class = "pln" > </span><span class = "pun" >/</span><span class = "pln" >etc</span><span class = "pun" >/</span><span class = "kwd" > default </span><span class = "pun" >/</span><span class = "pln" >grub </span><span class = "com" >#设置crashkernel=0M</span></li> <li class = "L2" ><span class = "pln" >sudo grub2</span><span class = "pun" >-</span><span class = "pln" >mkconfig </span><span class = "pun" >-</span><span class = "pln" >o </span><span class = "pun" >/</span><span class = "pln" >boot</span><span class = "pun" >/</span><span class = "pln" >grub2</span><span class = "pun" >/</span><span class = "pln" >grub</span><span class = "pun" >.</span><span class = "pln" >cfg </span><span class = "com" >#根据上述配置生成新的grub.cfg文件</span></li> </ol> |
修改后配置如下
/boot/grub2/grub.cfg的配置情况如下图 crashkernel=0M
修改前配置后内存使用情况如下
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 | <ol class = "linenums" > <li class = "L0" ><span class = "pun" >[</span><span class = "pln" >root @test </span><span class = "pun" >-</span><span class = "lit" > 1 </span><span class = "pln" > </span><span class = "pun" >~]#</span><span class = "pln" > free </span><span class = "pun" >-</span><span class = "pln" >m</span></li> <li class = "L1" ><span class = "pln" > total used free shared buffers cached</span></li> <li class = "L2" ><span class = "typ" >Mem</span><span class = "pun" >:</span><span class = "pln" > </span><span class = "lit" > 3696 </span><span class = "pln" > </span><span class = "lit" > 158 </span><span class = "pln" > </span><span class = "lit" > 3538 </span><span class = "pln" > </span><span class = "lit" > 8 </span><span class = "pln" > </span><span class = "lit" > 11 </span><span class = "pln" > </span><span class = "lit" > 72 </span></li> <li class = "L3" ><span class = "pun" >-</span><span class = "str" >/+ buffers/</span><span class = "pln" >cache</span><span class = "pun" >:</span><span class = "pln" > </span><span class = "lit" > 74 </span><span class = "pln" > </span><span class = "lit" > 3621 </span></li> <li class = "L4" ><span class = "typ" >Swap</span><span class = "pun" >:</span><span class = "pln" > </span><span class = "lit" > 0 </span><span class = "pln" > </span><span class = "lit" > 0 </span><span class = "pln" > </span><span class = "lit" > 0 </span></li> <li class = "L5" ><span class = "pun" >[</span><span class = "pln" >root @test </span><span class = "pun" >-</span><span class = "lit" > 1 </span><span class = "pln" > </span><span class = "pun" >~]#</span><span class = "pln" > dmesg </span><span class = "pun" >|</span><span class = "pln" > grep </span><span class = "typ" >Memory</span></li> <li class = "L6" ><span class = "pun" >[</span><span class = "pln" > </span><span class = "lit" > 0.000000 </span><span class = "pun" >]</span><span class = "pln" > </span><span class = "typ" >Memory</span><span class = "pun" >:</span><span class = "pln" > </span><span class = "lit" >4030504k</span><span class = "pun" >/</span><span class = "lit" >4456448k</span><span class = "pln" > available </span><span class = "pun" >(</span><span class = "lit" >6108k</span><span class = "pln" > kernel code</span><span class = "pun" >,</span><span class = "pln" > </span><span class = "lit" >262536k</span><span class = "pln" > absent</span><span class = "pun" >,</span><span class = "pln" > </span><span class = "lit" >163408k</span><span class = "pln" > reserved</span><span class = "pun" >,</span><span class = "pln" > </span><span class = "lit" >4071k</span><span class = "pln" > data</span><span class = "pun" >,</span><span class = "pln" > </span><span class = "lit" >1584k</span><span class = "pln" > init</span><span class = "pun" >)</span></li> <li class = "L7" ><span class = "pun" >[</span><span class = "pln" >root @test </span><span class = "pun" >-</span><span class = "lit" > 1 </span><span class = "pln" > </span><span class = "pun" >~]#</span><span class = "pln" > </span></li> </ol> |
通过对比可以看出
1、free -m 命令中total显示的总大小
修改前为3535M,修改后为3696M,变大了161M
2、 dmesg | grep Memory命令显示
系统保留reserved 减少了对应的大小修改前为328272k,修改后为163408k,减少了164864k,大小为161M
通过这样子配置后得到影响: