无限循环与boost :: asio :: deadline_timer C ++性能

Question

I develop a server application that handles many connections from clients. Server sends message to each clients periodically(ex: every 1 second), check for client's expiry times(each client must be disconnected from the server forcibly when connected time reaches a predetermined value) and some other timer tasks. I consider 2 solutions:

1. use while(true){foreach clients{check time}}
2. for each client, delcare a deadline_timer and call async_wait for each task, so it will spawn a lot of deadline_timer instances

Which solution is better for performance? In general, Should I use infinite loop or declaring many timer instances? And one more, Can you explain how OS manages deadline_timer?

Answer 1

Q. Which solution is better for performance?

Infinite loops are usually bad. Exceptions to be found in CPU-saturating workers with thread affinity (but that doesn't appear to be applicable here).

Q. In general, Should I use infinite loop

No

Q. or declaring many timer instances?

Or just

std::vector<boost::shared_ptr<asio::deadline_timer> > m_timers;

or similar :)

Q. And one more, Can you explain how OS manages deadlien_timer?

The timers are using platform specific kernel events, under the hood. Meaning, in practice, that if you have eg 10 tasks all blocked on different timers, the kernel will keep the process in sleep state (not running at all) until the first one expires.

Kernel-level synchronization primitives are in general the fastest way for non-CPU bound work loads, by far.

Answer 2

Do you require each client timeout at exactly(or almost) one second?

I would do third way:

while (true) {
  if ( elapsed_one_second() ) {
    for each client {
      client->check_timeout();
    }
}

Or if you have event queue, you do one timer to trigger the checking of all clients.

EDIT: If you have huge amount of timers, you may also consider implement a delta queue and use one-shot timer for the earliest event.