Get most duplicated strings from a heap dump using ClrMD

Get most duplicated strings from a heap dump using ClrMD

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ClrMD is an awesome managed API to inspect managed processes and dump files. To use it, just add a NuGet reference to Microsoft.Diagnostics.Runtime. When loading a dump, be sure to have the mscordacwks.dll from the machine where the dump was taken. Also make sure that your program that uses ClrMD is the same platform (32/64-bit) as the process/dump that you’re inspecting.

Here’s a sample of getting most duplicated strings out of a dump, an indication that you might need a string cache somewhere. Remember that if creating a dump of a 32-bit process on a 64-bit OS you need to use the 32-bit Task Manager, otherwise the dump will be useless.

using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.Diagnostics.Runtime;
 
namespace DumpTools
{
    class DumpHeapStrings
    {
        static void Main(string[] args)
        {
            using (var dataTarget = DataTarget.LoadCrashDump(@"app.dmp"))
            {
                var dacLocation = dataTarget.ClrVersions[0].TryGetDacLocation();
                var runtime = dataTarget.CreateRuntime(dacLocation);
                var heap = runtime.GetHeap();
                var objects = heap.EnumerateObjects();
 
                var stringUsages = new Dictionary<string, long>();
 
                foreach (var instance in objects.Take(1000000))
                {
                    var type = heap.GetObjectType(instance);
                    if (type != null && type.IsString)
                    {
                        var size = type.GetSize(instance);
                        var value = (string)type.GetValue(instance);
                        long usages = 0L;
                        if (stringUsages.TryGetValue(value, out usages))
                        {
                            stringUsages[value] = usages + 1;
                        }
                        else
                        {
                            stringUsages[value] = 1;
                        }
                    }
                }
 
                var sorted = stringUsages.OrderByDescending(kvp => kvp.Value).Take(100);
                foreach (var kvp in sorted)
                {
                    Console.WriteLine(kvp.Value + "\t\t" + kvp.Key);
                }
            }
        }
    }
}
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