-Xmx20m -Xms5m

比眉伴天荒 2024-03-17 16:43 123阅读 0赞

<table> 
 <thead> 
  <tr> 
   <th align="left"><strong>-Xms</strong></th> 
   <th align="left"><strong>java程序启动时<code>初始堆的大小</code>，默认是物理内存的<code>1/64</code></strong></th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td align="left"><strong>-Xmx</strong></td> 
   <td align="left"><strong>java程序能获得的<code>最大堆的大小</code>，默认为物理内存的<code>1/4</code></strong></td> 
  </tr> 
 </tbody> 
</table>

![在这里插入图片描述][475edd291cca40729a91087b25123f92.png_pic_center]

### 验证默认值 ###

<table> 
 <thead> 
  <tr> 
   <th align="left"><code>win+r</code> → <code>systeminfo</code></th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td align="left"><img src="https://img-blog.csdnimg.cn/e2c369ab42094d45a1dc58b450194003.png" alt="在这里插入图片描述"></td> 
  </tr> 
 </tbody> 
</table>

<table> 
 <thead> 
  <tr> 
   <th align="left">配置JVM启动参数：-XX:+PrintCommandLineFlags</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td align="left">-XX:ConcGCThreads=3 -XX:G1ConcRefinementThreads=13 -XX:GCDrainStackTargetSize=64 <code>-XX:InitialHeapSize=254884992</code> -XX:MarkStackSize=4194304 <code>-XX:MaxHeapSize=4078159872</code> -XX:MinHeapSize=6815736 -XX:+PrintCommandLineFlags -XX:ReservedCodeCacheSize=251658240 -XX:+SegmentedCodeCache -XX:+UseCompressedClassPointers -XX:+UseCompressedOops -XX:+UseG1GC -XX:-UseLargePagesIndividualAllocation</td> 
  </tr> 
  <tr> 
   <td align="left"></td> 
  </tr> 
  <tr> 
   <td align="left"><code>15557/64 = 243M</code> -Xms默认是物理内存的<code>1/64</code> 验证是对的</td> 
  </tr> 
  <tr> 
   <td align="left"><code>15557/4 = 3890M</code> -Xmx默认为物理内存的<code>1/4</code> 验证是对的</td> 
  </tr> 
 </tbody> 
</table>

Heap Configuration:
       MinHeapFreeRatio         = 40
       MaxHeapFreeRatio         = 70
       MaxHeapSize              = 4078960640 (3890.0MB)
       NewSize                  = 1363144 (1.2999954223632812MB)
       MaxNewSize               = 2447376384 (2334.0MB)
       OldSize                  = 5452592 (5.1999969482421875MB)
       NewRatio                 = 2
       SurvivorRatio            = 8
       MetaspaceSize            = 22020096 (21.0MB)
       CompressedClassSpaceSize = 1073741824 (1024.0MB)
       regions  = 1945
       capacity = 4078960640 (3890.0MB)
       used     = 4194304 (4.0MB)
       free     = 4074766336 (3886.0MB)
       0.10282776349614396% used
       
    G1 Young Generation:
    Eden Space:
       regions  = 2
       capacity = 25165824 (24.0MB)
       used     = 4194304 (4.0MB)
       free     = 20971520 (20.0MB)
       16.666666666666668% used
    Survivor Space:
       regions  = 0
       capacity = 0 (0.0MB)
       used     = 0 (0.0MB)
       free     = 0 (0.0MB)
       0.0% used
    G1 Old Generation:
       regions  = 0
       capacity = 230686720 (220.0MB)
       used     = 0 (0.0MB)
       free     = 230686720 (220.0MB)
       0.0% used

![在这里插入图片描述][475edd291cca40729a91087b25123f92.png_pic_center]

### 验证初始化值 ###

<table> 
 <thead> 
  <tr> 
   <th align="left">配置JVM启动参数：<code>-Xmx20m -Xms5m</code> -XX:+PrintCommandLineFlags</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td align="left"></td> 
  </tr> 
  <tr> 
   <td align="left">-XX:ConcGCThreads=3 -XX:G1ConcRefinementThreads=13 -XX:GCDrainStackTargetSize=64 <code>-XX:InitialHeapSize=5242880</code> -XX:MarkStackSize=4194304 <code>-XX:MaxHeapSize=20971520</code> -XX:MinHeapSize=5242880 -XX:+PrintCommandLineFlags -XX:ReservedCodeCacheSize=251658240 -XX:+SegmentedCodeCache -XX:+UseCompressedClassPointers -XX:+UseCompressedOops -XX:+UseG1GC -XX:-UseLargePagesIndividualAllocation</td> 
  </tr> 
  <tr> 
   <td align="left"></td> 
  </tr> 
 </tbody> 
</table>

[475edd291cca40729a91087b25123f92.png_pic_center]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/15/3bc140a8e20e4fd4af3c0cea7a40a302.png