So the subtraction of user input time from total time, namely the "real execution time", can truly reflect the user-perceived performance.

此时程序的“实际执行时间”，即整体执行时间与等待用户响应时间之差，才能够真实地反映用户可察觉的系统处理能力。

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Because of these features, the performance that is measured by a testing tool can differ from the performance that is perceived by the user.

由于这些特性的存在，测试工具测试的性能不同于用户预期的性能。

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The router can lazily preload modules after the app starts and before the user navigates to them for improved perceived performance.

路由器可以在应用启动之后和用户导航到惰性加载模块之前，预先加载惰性模块，以增强性能。

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