title: Why are "from space" and "to space" not equal in jvm
body: <ul>
  <li>environment:jdk8u101</li>
  <li>os:centos6</li>
  <li>describe: "from space" and "to space" are not equal eden of heap. In my mind, "from space" and "to space" use copy algorithm, their space will always remain equal.</li>
  <li>can someone help me?</li>
  <li>I couldn't paste the screenshot, so I stuck the main data below</li>
  </ul>
  
  <hr>
  
  <pre><code>[root@05c46b9d1fc1 /]# jmap -heap 1
  Attaching to process ID 1, please wait...
  Debugger attached successfully.
  Server compiler detected.
  JVM version is 25.101-b13
  
  using thread-local object allocation.
  Parallel GC with 33 thread(s)
  Heap Configuration:
     MinHeapFreeRatio         = 0
     MaxHeapFreeRatio         = 100
     MaxHeapSize              = 4294967296 (4096.0MB)
     NewSize                  = 357564416 (341.0MB)
     MaxNewSize               = 1431306240 (1365.0MB)
     OldSize                  = 716177408 (683.0MB)
     NewRatio                 = 2
     SurvivorRatio            = 8
     MetaspaceSize            = 21807104 (20.796875MB)
     CompressedClassSpaceSize = 1073741824 (1024.0MB)
     MaxMetaspaceSize         = 17592186044415 MB
     G1HeapRegionSize         = 0 (0.0MB)
  
  Heap Usage:
  PS Young Generation
  Eden Space:
     capacity = 342360064 (326.5MB)
     used     = 251910632 (240.2406997680664MB)
     free     = 90449432 (86.2593002319336MB)
     73.58061248639093% used
  From Space:
     capacity = 23068672 (22.0MB)
     used     = 0 (0.0MB)
     free     = 23068672 (22.0MB)
     0.0% used
  To Space:
     capacity = 44564480 (42.5MB)
     used     = 0 (0.0MB)
     free     = 44564480 (42.5MB)
     0.0% used
  PS Old Generation
     capacity = 763363328 (728.0MB)
     used     = 26507512 (25.27953338623047MB)
     free     = 736855816 (702.7204666137695MB)
     3.47246337722946% used
  </code></pre>