Java Verbose GC流程 <af = allocation failure 意思是分派内存失败

最新推荐文章于 2025-07-31 07:55:35 发布

最新推荐文章于 2025-07-31 07:55:35 发布 · 280 阅读

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本文深入探讨了Java中对象的内存分配过程及垃圾回收机制，详细解释了小对象区域、大对象区域和缓存区的工作原理，以及如何在不同场景下成功分配对象并避免内存溢出。

Verbose GC alwayshappen after Allocation Failure.

I. Object Allocation:

1. less than 512 bytes (768 bytes on 64-bit platforms) or Larger objects are allocated from the cache if they can be contained in the existing cache -> Cache allocation

2. If not satisfied in the existing cache -> Heap lock allocation -> Attempted in SOA (Small Object Area) at first:

2.1 ifsatisfy, Enjoy your new object!

2.2 if no satisfy, but object size is less than 512 bytes -> Allocation Failure (AF)

2.3 if no satisfy, but object size is large than 512 bytes -> Attempted inLOA (Large Object Area):
2.3.1 if satisfy, Enjoy your new object!
2.3.2 if no satisfy, Allocation Failure ->Registers a GC cycle

II. GC cycle

1) STW (Stop The World)
2) Reclaim spaces of un-reachable objects
3) Marking -> Sweeping -> Compaction(optional, one condition: not enough free space is available to satisfy the allocation request)

Yes - 1. Successful object allocation
2. Possible Heap Shrinkage
NO - Heap Expansion Possible?
Yes  Expand heap (Continuous), allocate object
No???  OutOfMemoryError (OOM)