注意：以下文档只适用于TOP接口，请谨慎使用！
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：
