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Update jvm-interviewanswer.md #20

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Expand Up @@ -669,7 +669,7 @@ Parallel Scavenge 的关注点主要在**达到一个可控制的吞吐量上面
* 重新标记（CMS remark）
* 并发清除（CMS concurrent sweep）

对于上面这四个步骤，初始标记和并发标记都需要 *Stop The World*，初始标记只是标记一下和 GC Roots 直接关联到的对象，速度较快；并发标记阶段就是从 GC Roots 的直接关联对象开始遍历整个对象图的过程。这个过程时间比较长但是不需要停顿用户线程，也就是说与垃圾收集线程一起并发运行。并发标记的过程中，可能会有错标或者漏标的情况，此时就需要在重新标记一下，最后是并发清除阶段，清理掉标记阶段中判断已经死亡的对象。
对于上面这四个步骤，初始标记和重新标记都需要 *Stop The World*，初始标记只是标记一下和 GC Roots 直接关联到的对象，速度较快；并发标记阶段就是从 GC Roots 的直接关联对象开始遍历整个对象图的过程。这个过程时间比较长但是不需要停顿用户线程，也就是说与垃圾收集线程一起并发运行。并发标记的过程中，可能会有错标或者漏标的情况，此时就需要在重新标记一下，最后是并发清除阶段，清理掉标记阶段中判断已经死亡的对象。

CMS 的收集过程如下

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