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copied!<p>Your latency will vary, but it will be far from the best you can get. Here are few things that will stand in your way to the better latency:</p> <p><strong>Boost.ASIO</strong></p> <ol> <li>It constantly allocates/deallocates memory to store "state" in order to invoke a callback function associated with your read operation.</li> <li>It does unnecessary <code>mutex</code> locking/unlocking in order to support a broken mix of async and sync approaches.</li> <li>The worst, it constantly adds and removes event descriptors from the underlying notification mechanism.</li> </ol> <p>All in all, <code>asio</code> is a good library for high-level application developers, but it comes with a big price tag and a lot of CPU cycle eating gremlins. Another alternative is <code>libevent</code>, it is a lot better, but still aims to support many notification mechanisms and be platform-independent. Nothing can beat native mechanisms, i.e. <code>epoll</code>.</p> <p><strong>Other things</strong></p> <ol> <li>UDP stack. It doesn't do a very good job for latency sensitive applications. One of the most popular solutions is OpenOnload. It by-passes the stack and works directly with your NIC.</li> <li>Scheduler. By default, scheduler is optimized for throughput and not latency. You will have to tweak and tune your OS in order to make it latency oriented. Linux, for example, has a lot of "rt" patches for that purpose.</li> <li>Watch out not to sleep. Once your process is sleeping, you will never get a good wakeup latency compared to constantly burning CPU and waiting for a packet to arrive.</li> <li>Interference with other IRQs, processes etc.</li> </ol> <p>I cannot tell you exact numbers, but assuming that you won't be getting a lot of traffic, using Boost and a regular Linux kernel, with a regular hardware, your latency will range somewhere between ~50 microseconds to ~100 milliseconds. It will improve a bit as you get more data, and after some point start dropping, and will always be ranging. I'd say that if you are OK with those numbers, don't bother optimizing.</p>

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