This way the web server can queue up all kinds of operations that were previously “expensive” syscalls by simply writing them to memory. In order to avoid busy looping, both the kernel and the web server will only busy-loop checking the queue for a little bit (configurable, but think milliseconds), and if there’s nothing new, the web server will do a syscall to “go to sleep” until something gets added to the queue. That way new connections don’t need syscalls, memory doesn’t get fragmented, and you don’t run the risk of running out of memory.