The GC can only contract contiguous blocks of memory from the end of the heap, so a compaction might be required to contract the heap.

GC 只能收缩从堆末尾开始的连续内存块，因此收缩堆可能需要进行压缩。

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Makes the compaction process more efficient and improves the end result: quality improvement, time and energy savings.

使压实过程更加有效，且提高的压实效果：即，质量提高了，而节约了时间和能源。

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