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POWhat are the reasons why the CPU usage doesn’t go 100% with C# and APM?
 

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  1. POWhat are the reasons why the CPU usage doesn’t go 100% with C# and APM?
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    <p>I have an application which is CPU intensive. When the data is processed on a single thread, the CPU usage goes to 100% for many minutes. So the performance of the application appears to be bound by the CPU. I have multithreaded the logic of the application, which result in an increase of the overall performance. However, the CPU usage hardly goes above 30%-50%. I would expect the CPU (and the many cores) to go to 100% since I process many set of data at the same time.</p> <p>Below is a simplified example of the logic I use to start the threads. When I run this example, the CPU goes to 100% (on an 8/16 cores machine). However, my application which uses the same pattern doesn’t.</p> <pre><code>public class DataExecutionContext { public int Counter { get; set; } // Arrays of data } static void Main(string[] args) { // Load data from the database into the context var contexts = new List&lt;DataExecutionContext&gt;(100); for (int i = 0; i &lt; 100; i++) { contexts.Add(new DataExecutionContext()); } // Data loaded. Start to process. var latch = new CountdownEvent(contexts.Count); var processData = new Action&lt;DataExecutionContext&gt;(c =&gt; { // The thread doesn't access data from a DB, file, // network, etc. It reads and write data in RAM only // (in its context). for (int i = 0; i &lt; 100000000; i++) c.Counter++; }); foreach (var context in contexts) { processData.BeginInvoke(context, new AsyncCallback(ar =&gt; { latch.Signal(); }), null); } latch.Wait(); } </code></pre> <p>I have reduced the number of locks to the strict minimum (only the latch is locking). The best way I found was to create a context in which a thread can read/write in memory. Contexts are not shared among other threads. The threads can’t access the database, files or network. In other words, I profiled my application and I didn’t find any bottleneck.</p> <p>Why the CPU usage of my application doesn’t go about 50%? Is it the pattern I use? Should I create my own thread instead of using the .Net thread pool? Is there any gotchas? Is there any tool that you could recommend me to find my issue?</p> <p>Thanks!</p>
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    1. COPossible, but quite unlikely would be that your code is triggering a lot of garbage collection, which requires some amount of synchronization.
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