JVM 的内存占用到底怎么看呢，为何 jmap 和 top 差这么多

现在 JVM 在 TOP 里面占用了 969MB，担心哪一天内存不够用了，想排查一下。

6033 root      20   0 4839404 992584   9932 S  0.3 51.7   9:59.60 java  

然后看了下 jmap

Heap Configuration:
   MinHeapFreeRatio         = 40
   MaxHeapFreeRatio         = 70
   MaxHeapSize              = 492830720 (470.0MB)
   NewSize                  = 10485760 (10.0MB)
   MaxNewSize               = 164233216 (156.625MB)
   OldSize                  = 20971520 (20.0MB)
   NewRatio                 = 2
   SurvivorRatio            = 8
   MetaspaceSize            = 21807104 (20.796875MB)
   CompressedClassSpaceSize = 1073741824 (1024.0MB)
   MaxMetaspaceSize         = 17592186044415 MB
   G1HeapRegionSize         = 0 (0.0MB)

Heap Usage:
New Generation (Eden + 1 Survivor Space):
   capacity = 87752704 (83.6875MB)
   used     = 68565312 (65.38897705078125MB)
   free     = 19187392 (18.29852294921875MB)
   78.13469998599702% used
Eden Space:
   capacity = 78053376 (74.4375MB)
   used     = 63509624 (60.56749725341797MB)
   free     = 14543752 (13.870002746582031MB)
   81.36691486605268% used
From Space:
   capacity = 9699328 (9.25MB)
   used     = 5055688 (4.821479797363281MB)
   free     = 4643640 (4.428520202636719MB)
   52.12410591744088% used
To Space:
   capacity = 9699328 (9.25MB)
   used     = 0 (0.0MB)
   free     = 9699328 (9.25MB)
   0.0% used
tenured generation:
   capacity = 194756608 (185.734375MB)
   used     = 157623088 (150.3210906982422MB)
   free     = 37133520 (35.41328430175781MB)
   80.93337094883066% used

27656 interned Strings occupying 2127192 bytes.

在 jstat -gc 里面看 Meta 区的占用 是 68M

 S0C    S1C    S0U    S1U      EC       EU        OC         OU       MC     MU    CCSC   CCSU   YGC     YGCT    FGC    FGCT     GCT   
9472.0 9472.0  0.0    0.0   76224.0  40490.7   190200.0   114119.8  70272.0 67888.9 8320.0 7522.7    923    9.428  26      4.113   13.540

发现实际上也就只用了 83.68+185.73+68 = 337.4 MB 而已

这方面没有经验，有没有大佬指点一下，内存到底跑哪去了呢。