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POinterlock vs mutex, scale-up issues
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copied!<p>I am facing the problem, that I have an C# (.NET) object shared among some threads. A thread might replace the object with another one. The threads are waken up from a TCP/IP connection using the Asynchronous framework.</p> <h2>Sequence:</h2> <p>Threads (waiting for connection) -> Asynchronous Callback -> Do something thread-safe -> Access the shared object -> Do something thread-safe.</p> <h2>1. Solution Mutex:</h2> <pre><code>Object sharedObject = new Object(); Mutex objectMutex = new Mutex(); void threadCallback() { Object newObject = new Object(); // some processing objectMutex.lock(); // do exchange sharedObject with newObject if needed // very little processing here objectMutex.unlock(); // some processing } </code></pre> <h2>2. Solution Interlock</h2> <pre><code>Object sharedObject = new Object(); int usingSharedObject = 0; void threadCallback() { Object newObject = new Object(); // some processing // poll until we lock while(1 == Interlocked.Exchange(ref usingSharedObject , 1)) { // do exchange sharedObject with newObject if needed // very little processing here Interlocked.Exchange(ref usingSharedObject , 0); // free lock } // some processing } </code></pre> <h2>What is faster and scales up better?</h2> <p>I expect the second solution to be faster as long as there are not to many threads polling at the same time. The second solution might even sleep a random time so that polling does not eat up any processing time. The first solution looks cleaner to me if I really do need to process a lot of TCP/IP connections. Since I do very little processing in the locked section regarding the TCP/IP processing, will there be any scale-up-issues? </p> <h2>How about the object creation at the beginning of the threadCallback() function.</h2> <p>In my C++ background I always used memory-pools in such a situation, since I must use safe .NET is there a fast way to create new Objects or does the .NET platform perform well in this field. </p> <p>Best regards,</p> <p>Friedrich</p>

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