Volatile vs. Interlocked vs. lock

Question

Let\'s say that a class has a public int counter field that is accessed by multiple threads. This int is only incremented or decremented.

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Answer 1

I did some test to see how the theory actually works: kennethxu.blogspot.com/2009/05/interlocked-vs-monitor-performance.html. My test was more focused on CompareExchnage but the result for Increment is similar. Interlocked is not necessary faster in multi-cpu environment. Here is the test result for Increment on a 2 years old 16 CPU server. Bare in mind that the test also involves the safe read after increase, which is typical in real world.

D:\>InterlockVsMonitor.exe 16
Using 16 threads:
          InterlockAtomic.RunIncrement         (ns):   8355 Average,   8302 Minimal,   8409 Maxmial
    MonitorVolatileAtomic.RunIncrement         (ns):   7077 Average,   6843 Minimal,   7243 Maxmial

D:\>InterlockVsMonitor.exe 4
Using 4 threads:
          InterlockAtomic.RunIncrement         (ns):   4319 Average,   4319 Minimal,   4321 Maxmial
    MonitorVolatileAtomic.RunIncrement         (ns):    933 Average,    802 Minimal,   1018 Maxmial