从文档一>关于 noHistory ：

的真则表示该活动不会留下历史痕迹。它不会留在任务的活动栈，因此，用户将不能够返回到它。

A value of "true" means that the activity will not leave a historical trace. It will not remain in the activity stack for the task, so the user will not be able to return to it.

关于你的问题：

确实的A，B，A，B，A，B真栈的存在？

does the true stack of A, B, A, B, A, B exist?

该文档就表示没有。

我很担心资源问题，而不是放慢一个用户的Andr​​oid设备。

I'm concerned with resource issues and not slowing down a users android device.

您真的不需要担心这个。操作系统应该处理的活动，清理时，存储空间不足。它更可能是穷人用你们的活动位图或逻辑会导致性能下降。

You really don't need to worry about this. The OS should handle the cleanup of activities when memory is getting low. Its more likely that poor use of bitmaps or logic in your activities will result in performance slowdowns.