The Sun JDKs use an optimized variant of an algorithm called card marking to identify modifications to pointers held in fields of old-generation objects.

Sun JDK 使用一种称为 卡片标记（card marking）算法的改进算法以标识对老一代对象的字段中包含的指针的修改。

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There are several costs to card marking - additional space for the card map, additional work to be done on each pointer store, and additional work to be done at garbage collection time.

卡片标记有几项开销——卡片映射所需的额外空间、对每一个指针存储所做的额外工作，以及在垃圾收集时做的额外工作。

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Card marking algorithms can add as little as two or three machine instructions per non-initializing heap pointer store, and entails scanning any objects on dirty CARDS at minor collection time.

对每一个非初始化堆指针存储，卡片标记算法可以只增加两到三个机器指令，并要求在小的收集时对所有脏卡片上的对象进行扫描。

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