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    <p>100 is far too few, and running in a test framework may skew things. It is also possibly (see comments) related to any additional cost associated with the <em>first</em> lock against an object; try:</p> <ul> <li>locking once outside the loop first</li> <li>doing lots more iterations</li> <li>in a console exe, at the command line, in release mode</li> </ul> <p>Also, note that in 4.0 <code>lock</code> is <strong>not</strong> <code>Monitor.Enter(object)</code> - so expect different results in 4.0.</p> <p>But I get:</p> <pre><code>lock: 3548ms Monitor.TryEnter: 7008ms Monitor.TryEnter (2): 2947ms Monitor.Enter: 2906ms </code></pre> <p>From the test rig:</p> <pre><code>using System; using System.Diagnostics; using System.Threading; static class Program { static void Main() { const int lockIterations = 50000000; object object1 = new object(); lock (object1) { Console.WriteLine("First one has to pay an extra toll"); } Stopwatch csLock = Stopwatch.StartNew(); for (int i = 0; i &lt; lockIterations; ) { lock (object1) { i++; } } csLock.Stop(); Console.WriteLine("lock: " + csLock.ElapsedMilliseconds + "ms"); Stopwatch csMonitorTryEnter = Stopwatch.StartNew(); for (int i = 0; i &lt; lockIterations; ) { if (Monitor.TryEnter(object1, TimeSpan.FromSeconds(10))) { try { i++; } finally { Monitor.Exit(object1); } } } csMonitorTryEnter.Stop(); Console.WriteLine("Monitor.TryEnter: " + csMonitorTryEnter.ElapsedMilliseconds + "ms"); csMonitorTryEnter = Stopwatch.StartNew(); for (int i = 0; i &lt; lockIterations; ) { if (Monitor.TryEnter(object1, 10000)) { try { i++; } finally { Monitor.Exit(object1); } } } csMonitorTryEnter.Stop(); Console.WriteLine("Monitor.TryEnter (2): " + csMonitorTryEnter.ElapsedMilliseconds + "ms"); Stopwatch csMonitorEnter = Stopwatch.StartNew(); for (int i = 0; i &lt; lockIterations; ) { Monitor.Enter(object1); try { i++; } finally { Monitor.Exit(object1); } } csMonitorEnter.Stop(); Console.WriteLine("Monitor.Enter: " + csMonitorEnter.ElapsedMilliseconds + "ms"); } } </code></pre>
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    1. POWhy is lock much slower than Monitor.TryEnter?
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    1. USMarc Gravell
    1. USMarc Gravell
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      1. VTUpMod
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    1. COI thought the full "thick" monitor was only set up on the first *contended* lock? Otherwise doesn't it just use a flag in the syncblock?
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      1. USJon Skeet
    2. CO@Jon - maybe; brain fuzzy - I'll mark that "in doubt"
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      1. USMarc Gravell
    3. COMarc, have go got any references to prove that 'in 4.0 lock is not Monitor.Enter'. That seems highly unlikely to me.
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      1. USSteven
 

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