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Can the thread per request model be faster than non-blocking I/O?

Asked 2011-02-08T04:47:31.223
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I remember 2 or 3 years ago reading a couple articles where people claimed that modern threading libraries were getting so good that thread-per-request servers would not only be easier to write than non-blocking servers but that they'd be faster, too. I believe this was even demonstrated in Java with a JVM that mapped Java threads to pthreads (i.e. the Java nio overhead was more than the context-switching overhead).

But now I see all the "cutting edge" servers use asynchronous libraries (Java nio, epoll, even node.js). Does this mean that async won?

java multithreading pthreads nio
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It is faster as long as there is enough memory.

When there are too many connections, most of which are idle, NIO can save threads therefore save memory, and the system can handle a lot more users than thread-per-connection model.

CPU is not a direct factor here. With NIO, you effectively need to implement a threading model yourself, which is unlikely to be faster than JVM's threads.

In either choice, memory is the ultimate bottleneck. When load increases and memory used approaches max, GC will be very busy, and the system often demonstrate the symptom of 100% CPU.

answered 2011-02-08T04:53:59.323

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