Daily Archives: September 13, 2007

How to measure memory use in .Net programs

In developing an important component (which I will discuss soon) for my current personal project, there were a number of different algorithms which I could use to attack the problem. I wasn’t sure which one would be better so I decided to implement each of them and measure their time/memory usage. I have a series of articles planned on those, but first I need to mention how I did the measurement.


For the timing, I simply wrapped the API functions for QueryPerformanceCounter and QueryPerformanceFrequency into a C# class. There are plenty of examples out there on the net to do this.

The memory usage is even simpler. The function you need is GC.GetTotalMemory(bool forceFullCollection). This function returns the amount of memory allocated. The little program below demonstrates how to use it.

using System;

namespace MemUsageTest
    class Program
        static void Main(string[] args)
            long memStart = GC.GetTotalMemory(true);
            Int32[] myInt = new Int32[4];
            long memEnd = GC.GetTotalMemory(true);

            long diff = memEnd - memStart;

            Console.WriteLine("{0:N0} bytes used", diff);

The output on my 32-bit system is “40 bytes used”–16 bytes for integers and 24 bytes of array overhead.

Passing true to GetTotalMemory is important–it gives the garbage collector an opportunity to reclaim all unused memory. There is a caveat, though. If you read the documentation, you’ll notice it says it attempts to discover the amount of bytes in use, and that setting forceFullCollection only gives it an opportunity and waiting a bit before returning. It does NOT guarantee that all unused memory is reclaimed.

As far as my work goes, I’ve noticed that it does a pretty reliable and consistent job.

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