内核到用户空间的低延迟通信-Kerneltouserspacecommunicationwithlowlatency

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The interrupt handler could write directly into a mapped memory range provided by the process, while the process is busy-waiting for that memory location to change. This can even be performed in the top-half and should provide you with the lowest latency possible. Make sure, that the memory location provided is locked into physical memory, since it cannot be paged in during the isr.

中断处理程序可以直接写入进程提供的映射内存范围，而进程则忙于等待该内存位置的更改。这甚至可以在上半部分执行，并且应该为您提供尽可能低的延迟。确保所提供的内存位置被锁定在物理内存中，因为在isr中不能对其进行分页。

Similar approaches can be found with packet sockets and PACKET_MMAP, where communication between kernel and userspace takes place through a shared memory space (see the Kernel Documentation).

包套接字和PACKET_MMAP也有类似的方法，内核和用户空间之间通过共享内存空间进行通信(请参阅内核文档)。

If you do not care about resource management through the OS (because you only have a single application waiting for external input), you could also choose to directly access the hardware from userspace (with iopl/inb/outb and friends).

如果您不关心通过OS进行资源管理(因为您只有一个应用程序等待外部输入)，您还可以选择直接从userspace(使用iopl/inb/outb和friends)访问硬件。

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A standard way for the process to wait for the kernel to wake it is to use the poll() system call and for your device driver's interrupt handler to wake any threads waiting for it.

进程等待内核唤醒的标准方法是使用poll()系统调用和设备驱动程序的中断处理程序唤醒等待它的任何线程。

The longest latency operation listed in your 4 bullets is waking the application thread, so if you need even shorter latency you need the thread to be awake but waiting for the event.

在您的4个项目中列出的最长延迟操作是唤醒应用程序线程，因此如果您需要更短的延迟，您需要线程处于清醒状态，但需要等待事件。

The lowest latency mechanism I have used is to have the interrupt write a word in the application process and to have a thread reading that word and proceeding when the value is changed. In effect, a spin lock between user space and kernel space. Use this mechanism when you can dedicate a CPU core to the spin lock or when you expect the waiting time to be very short.

我使用的最低延迟机制是让中断在应用程序进程中编写一个单词，并让线程读取该单词并在值更改时继续执行。实际上，用户空间和内核空间之间的自旋锁。当您可以将CPU核心用于自旋锁时，或者当您预期等待时间非常短时，请使用此机制。

You can use an ioctl() to pass in a user space pointer to the driver so it knows which word to update.

您可以使用ioctl()将用户空间指针传递给驱动程序，以便它知道要更新哪个单词。