Question

我们偶然发现了Quartz Events的性能问题，更具体地说是CGEventPost：在繁重的GPU加载期间，CGEventPost可能会阻塞。我们创建了a small benchmark application to demonstrate the issue。此应用程序只是一个创建，发布和发布事件的循环。

您可以在下面看到运行该应用程序的结果。第一次运行是在空闲系统上。第二次运行是使用FurMark（GPU压力测试），拨号盘尽可能地增加。

内部是内循环所需的时间，基本上只是使用Quartz Events创建，发布和发布事件。
外面是我们的节目等待被唤醒的时间（睡眠）。应该接近我们睡觉的时间，但如果系统承受压力，可能会延迟。
帖子是活动发布的时间。

18:58:01.683 EventPerformance[4946:707] Measurements: (outer should be close to 10)
18:58:01.684 EventPerformance[4946:707] inner (ms): 0.04, outer (ms): 11.02, CGEventPost (ms): 0.03
18:58:01.684 EventPerformance[4946:707] inner (ms): 0.04, outer (ms): 11.02, CGEventPost (ms): 0.03
18:58:01.685 EventPerformance[4946:707] inner (ms): 0.07, outer (ms): 10.26, CGEventPost (ms): 0.03
18:58:01.685 EventPerformance[4946:707] inner (ms): 0.06, outer (ms): 10.85, CGEventPost (ms): 0.05
18:58:01.686 EventPerformance[4946:707] inner (ms): 0.07, outer (ms): 10.41, CGEventPost (ms): 0.04
18:58:01.686 EventPerformance[4946:707] inner (ms): 0.04, outer (ms): 10.39, CGEventPost (ms): 0.03
18:58:01.686 EventPerformance[4946:707] inner (ms): 0.05, outer (ms): 11.02, CGEventPost (ms): 0.03
18:58:01.687 EventPerformance[4946:707] inner (ms): 0.03, outer (ms): 10.67, CGEventPost (ms): 0.03
18:58:01.687 EventPerformance[4946:707] inner (ms): 0.08, outer (ms): 10.09, CGEventPost (ms): 0.05
18:58:01.688 EventPerformance[4946:707] Averages: (outer should be close to 10)
18:58:01.688 EventPerformance[4946:707] avg inner (ms): 0.05, avg outer (ms): 10.64, avg post (ms): 0.03

在这里，我们可以看到发布事件的平均时间约为0.03毫秒。此外，线程似乎也在0.5ms左右被唤醒。 CGEventPost没有峰值。

19:02:02.150 EventPerformance[5241:707] Measurements: (outer should be close to 10)
19:02:02.151 EventPerformance[5241:707] inner (ms): 0.03, outer (ms): 10.23, CGEventPost (ms): 0.02
19:02:02.151 EventPerformance[5241:707] inner (ms): 0.02, outer (ms): 10.54, CGEventPost (ms): 0.02
19:02:02.151 EventPerformance[5241:707] inner (ms): 0.02, outer (ms): 11.01, CGEventPost (ms): 0.01
19:02:02.152 EventPerformance[5241:707] inner (ms): 0.02, outer (ms): 10.74, CGEventPost (ms): 0.01
19:02:02.152 EventPerformance[5241:707] inner (ms): 0.02, outer (ms): 10.20, CGEventPost (ms): 0.01
19:02:02.152 EventPerformance[5241:707] inner (ms): 10.35, outer (ms): 11.01, CGEventPost (ms): 10.35
19:02:02.152 EventPerformance[5241:707] inner (ms): 0.03, outer (ms): 10.02, CGEventPost (ms): 0.02
19:02:02.153 EventPerformance[5241:707] inner (ms): 58.90, outer (ms): 10.11, CGEventPost (ms): 58.90
19:02:02.153 EventPerformance[5241:707] inner (ms): 0.03, outer (ms): 10.12, CGEventPost (ms): 0.02
19:02:02.153 EventPerformance[5241:707] Averages: (outer should be close to 10)
19:02:02.371 EventPerformance[5241:707] avg inner (ms): 7.71, avg outer (ms): 10.44, avg post (ms): 7.71

当系统负载过重时，发布事件可能会占用（峰值）毫秒而不是微秒。在极端GPU压力（<1 FPS）下，此值可能需要几秒钟。 CGEventPost 有时似乎在等待GPU在返回之前完成一些工作。我们的线程仍然正常安排，没有明显的延迟/尖峰（外部）。

任何想法都表示赞赏。

Answer 1

我猜你正在填补队列（底层马赫端口）......

您可以使用仪器中的“调度”或“系统调用”仪器进行确认。（创建一个新的空白文档，添加仪器，然后在File > Record Options...下确保选中“延迟模式”。）这将显示应用程序中的所有线程活动（线程阻塞，睡眠时，激活时），以及为什么）。

我首先尝试提高调用man 3 PTHREAD_SCHEDPARAM的线程的线程优先级（参见CGEventPost）。如果你的线程在较低优先级的线程上被阻塞，内核应该暂时提升阻塞线程的优先级，以避免优先级倒置，并帮助你的任务提前完成。

总体而言，我认为您必须实施 2线程解决方案，如下所示：

为要发布的事件创建队列。从主线程（或事件发布线程）将事件发布到此队列，然后发出第二个线程（您创建的事件使用者线程）的信号，以便遍历队列并使用CGEventPost发布任何未完成的事件。

当CGEventPost阻止时，您的第二个事件发布线程将阻止，但这不会阻止任何其他线程。当CGEventPost最终解除阻塞时，它将使用您的事件使用者线程发布的任何未完成事件，并且事件使用者线程可以恢复发布事件。

另一种可能性：你能举办活动吗？某些类型的事件（鼠标移动？）可以用来减少事件。您有时可能会遇到CGEventPost的队列限制，我认为2线程方法可能是您最好的选择。

GPU负载下CGEventPost性能不佳

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