1.分析日志环境:

新生代总大小：2001856K 
eden区：1906560K
survivor的from or to区：95296K
老年代区：2097152K

2.开始分析6(系紧安全带)：

{Heap before GC invocations=352 (full 0):
 par new generation   total 2001856K, used 1912508K 
  [0x00000006ed400000, 0x000000076d400000, 0x000000076d400000)
     <!-- total表示新生代总大小2001856K，新生代被占用总大小1912508K -->
  eden space 1906560K, 100% used 
  [0x00000006ed400000, >>0x00000007619e0000, 0x00000007619e0000)
     <!--  eden区大小1906560K -->
  from space 95296K,   6% used 
  [0x00000007619e0000, 0x0000000761faf2f0, 0x00000007676f0000)
  to   space 95296K,   0% used 
  [0x00000007676f0000, 0x00000007676f0000, 0x000000076d400000)
     <!--  from or to区大小95296K -->
     <!--  此处公式eden+(from or to) = 新生代总大小 -->
 concurrent mark-sweep generation total 2097152K, used 605158K 
  [0x000000076d400000, 0x00000007ed400000, 0x00000007ed400000)
 concurrent-mark-sweep perm gen total 307200K, used 143843K 
  [0x00000007ed400000, 0x0000000800000000, 0x0000000800000000)
     <!--  到此为止都是gc(yonggc)前的内存快照信息 -->
2018-04-16T14:21:01.372+0800: 356430.769: 
  [GC2018-04-16T14:21:01.372+0800: 356430.769: 
    [ParNew2018-04-16T14:21:01.388+0800: 356430.785: 
      [SoftReference, 0 refs, 0.0000430 secs]2018-04-16T14:21:01.388+0800: 356430.785: 
      [WeakReference, 15 refs, 0.0000150 secs]2018-04-16T14:21:01.388+0800: 356430.785: 
      [FinalReference, 88 refs, 0.0000630 secs]2018-04-16T14:21:01.388+0800: 356430.785: 
      [PhantomReference, 0 refs, 0.0000100 secs]2018-04-16T14:21:01.388+0800: 356430.785: 
      [JNI Weak Reference, 0.0000100 secs]
      <!--  gc清理所有引用信息 -->
  Desired survivor size 48791552 bytes, new threshold 10 (max 10)
      <!--  48791552指的是survivor 的1/2 或者说是一个from or to 区域的大小 -->
  - age   1:    1041056 bytes,    1041056 total
  - age   2:      28800 bytes,    1069856 total
  - age   3:      17352 bytes,    1087208 total
  - age   4:      10992 bytes,    1098200 total
  - age   5:      96456 bytes,    1194656 total
  - age   6:      52200 bytes,    1246856 total
  - age   7:      82456 bytes,    1329312 total
  - age   8:     940424 bytes,    2269736 total
  - age   9:     789088 bytes,    3058824 total
  - age  10:      18736 bytes,    3077560 total
     <!--  totalsize是所有年龄的对象大小的总和，这里有个隐含的点：
        当总totalsize>(Desired survivor size) 时，对象threashold会修改 -->
:1912508K->4950K(2001856K), 0.0161230 secs]2517666K->611978K(4099008K), 0.0163910 secs] 
    [Times: user=0.05 sys=0.00, real=0.02 secs]
     <!--  1912508K表示被占用的eden区->经过回收后剩余大小4950K，
      2001856K表示新生代总大小。总共被使用的堆大小2517666K->经过回收后占用大小611978K，
      4099008K表示堆总大小 -->
Heap after GC invocations=353 (full 0):
  par new generation   total 2001856K, used 4950K 
  [0x00000006ed400000, 0x000000076d400000, 0x000000076d400000)
     <!--  新生代总大小2001856K，使用4950K -->
  eden space 1906560K,   0% used
  [0x00000006ed400000, 0x00000006ed400000, 0x00000007619e0000)
     <!--  eden区大小1906560K，使用百分比 -->
  from space 95296K,   5% used 
  [0x00000007676f0000, 0x0000000767bc5808, 0x000000076d400000)
     <!--  survivor区from大小95296K，使用百分比 -->
  to   space 95296K,   0% used 
  [0x00000007619e0000, 0x00000007619e0000, 0x00000007676f0000)
     <!--  survivor区to大小95296K，使用百分比 -->
  concurrent mark-sweep generation total 2097152K, 
    used 607028K [0x000000076d400000, 0x00000007ed400000, 0x00000007ed400000)
     <!--  老年代区大小2097152K，使用了607028K -->
  concurrent-mark-sweep perm gen total 307200K, 
    used 143843K [0x00000007ed400000, 0x0000000800000000, 0x0000000800000000)
      <!--  perm区大小307200K，使用了143843K -->
}