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。
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.
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。
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.
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。
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.
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