Use of linux timerfd for implementing timeouts in Dev poll reactor

Question

Was just wondering whether use of timerfd (timerfd_create) for linux would give any performance benefit over Timer_Heap or Timer_Wheel. Surely, this is a very high level question and the only place I have seen it being used in any framework is "muduo".Also, I don't have any performance comparisons as well.

Thanks.

Answer 1

Event-loop libraries like libevent, maintain the timers in a min-heap and pass the timeout till the next timer expiry to select/epoll. Note that adding and removing a timer does not involve any system calls in this scenario, it just adds a new element into the min-heap.

When you use timerfd, it takes 3 system calls (timerfd_create(), timerfd_settime() and epoll_ctl()) just to create a timer. And every time it expires you need to read() from that file descriptor.

timerfd could be useful for applications without an event loop, but for ones that already use a decent event loop it is pretty much useless.