The difference between horizontal and edge triggering

Horizontal triggering (level-triggered, also known as conditional triggering) LT:triggers an event whenever a condition is met (the kernel keeps you informed as long as the data is not being fetched)

Edge Trigger (edge-triggered) ET: an event is triggered whenever the state changes.
"to read the socket example, assume that after a long period of silence, there are now 100 bytes, and both the edge trigger and the conditional trigger will produce a read Ready notification notification application. The application reads 50 bytes and then calls the API again to wait for the IO event. The condition-triggered API will now return the user to a read ready notification because it is still 50 bytes readable. The edge-triggered API is stuck for long waits because the readable state does not change. So when using edge-triggered APIs, be aware that each time you read the socket back to ewouldblock, otherwise the socket is obsolete. When using the conditional-triggered API, do not focus on the socket writable event if the application does not need to write, or it will return a write ready notification an unlimited number of times. We commonly use SELECT is a conditional trigger this category, long-term concern socket write event will appear CPU 100% problem.

The difference between horizontal and edge triggering