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    <p>If using native libraries <a href="http://bit.ly/lp1YnP" rel="nofollow">via JNI</a> is an option, I'd consider implementing IPC as usual (search for IPC, mmap, shm_open, etc.).</p> <p>There's a lot of overhead associated with using JNI, but at least it's a little less than the full system calls needed to do anything with sockets or pipes. You'll likely be able to get down to about 3 microseconds one-way latency using a polling shared memory IPC implementation via JNI. (Make sure to use the -Xcomp JVM option or adjust the compilation threshold, too; otherwise your first 10,000 samples will be terrible. It makes a big difference.)</p> <p>I'm a little surprised that a TCP socket write is taking 50 microseconds - most operating systems optimize TCP loopback to some extent. Solaris actually does a pretty good job of it with something called <a href="http://bit.ly/lskzRx" rel="nofollow">TCP Fusion</a>. And if there <em>has</em> been any optimization for loopback communication at all, it's usually been for TCP. UDP tends to get neglected - so I wouldn't bother with it in this case. I also wouldn't bother with pipes (stdin/stdout or your own named pipes, etc.), because they're going to be even slower.</p> <p>And generally, a lot of the latency you're seeing is likely coming from signaling - either waiting on an IO selector like select() in the case of sockets, or waiting on a semaphore, or waiting on something. If you want the lowest latency possible, you'll have to burn a core sitting in a tight loop polling for new data.</p> <p>Of course, there's always the <a href="http://bit.ly/iEewhc" rel="nofollow">commercial off-the-shelf</a> route - which I happen to know for a certainty would solve your problem in a hurry - but of course it does cost money. And in the interest of full disclosure: I do work for Informatica on their low-latency messaging software. (And my honest opinion, as an engineer, is that it's pretty fantastic software - certainly worth checking out for this project.)</p>
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    1. POJava TCP/IP Socket Latency - stuck at 50 μs (microseconds)? (used for Java IPC)
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    1. COI checked out your website and saw your ultra messaging product. I saw that on CISCO UCS it is showing latency less than 1 μs. What do you think it would be on a standard Linux server? (e.g. 2 dual core intel Xeon)?
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      1. USSam Goldberg
    2. COI've actually tested here with a dinky Core 2 Quad Q6600 machine I bought for about $400, and I can get under 1 microsecond on that in C, too (just a little under, though - it's still not nearly as impressive as the fancier Cisco server machine could do). The under-one-microsecond numbers are all from benchmarks run with plain C apps; for Java, add a couple microseconds as a basic floor due to the JNI overhead. And that's also with a receiving thread that's polling in a tight loop; you can run it non-polling too, but then you get a few more micros of signaling/thread wakeup latency.
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