jvm内存不足导致应用僵死问题咨询

Question

页面上操作无反应 应用好像僵死

在服务器上执行Top

  PID USER      PR  NI    VIRT    RES    SHR S %CPU %MEM     TIME+ COMMAND
 2299 root      20   0 2621076 727936  16544 S 99.9 38.6  67:08.05 java
 

看到CPU100% 都是mongo 查询和插入的操作 没有计算密集型的操作 怎么会CPU100%呢

jstack看到的几乎都是BLOCKED状态

Thread 21304: (state = BLOCKED)

查看 jmap -heap 2299

Heap Usage:
New Generation (Eden + 1 Survivor Space):
   capacity = 144703488 (138.0MB)
   used     = 132853872 (126.69932556152344MB)
   free     = 11849616 (11.300674438476562MB)
   91.81110547936481% used
Eden Space:
   capacity = 128647168 (122.6875MB)
   used     = 128647168 (122.6875MB)
   free     = 0 (0.0MB)
   100.0% used
From Space:
   capacity = 16056320 (15.3125MB)
   used     = 4206704 (4.0118255615234375MB)
   free     = 11849616 (11.300674438476562MB)
   26.199677136479593% used
To Space:
   capacity = 16056320 (15.3125MB)
   used     = 0 (0.0MB)
   free     = 16056320 (15.3125MB)
   0.0% used
tenured generation:
   capacity = 321585152 (306.6875MB)
   used     = 244174704 (232.86314392089844MB)
   free     = 77410448 (73.82435607910156MB)
   75.92847570275882% used

怀疑是内存不足导致应用僵死
为什么会僵死 而不是直接抛内存溢出（OutOfMemory）异常呢？为什么CPU会100%呢？

Answer 1

可能是代码不停的创建没用的对象，不停的触发GC回收这些没用的对象，导致程序僵死，查查看GC回收的是什么对象。