This tool shows list of owners for specific .NET object in GC Heap from full memory dump file.
Supported environments (Tested.)
* .NET Framework 4.6.1 or later
* Windows 10 or later
It will help to track memory-leaked object from dump file. For example, let's try this example,
using System;
using System.Collections.Generic;
namespace ConsoleApp1
{
class Program
{
static List<string> _list = new List<string>();
static void Main(string[] args)
{
CreateObjects();
GC.Collect(2);
GC.Collect(2);
Console.WriteLine("Dump!");
Console.ReadKey();
}
private static void CreateObjects()
{
for (int i = 0; i < 100000; i ++)
{
_list.Add(Guid.NewGuid().ToString());
}
}
}
}
Run and take full memory dump file. For analyzing, you can run windbg with SOS extension, then you can find System.String seems to leak with "!dumpheap -stat" command.
0:000> !dumpheap -stat
Statistics:
MT Count TotalSize Class Name
719025c4 1 12 System.Collections.Generic.GenericEqualityComparer`1[[System.String, mscorlib]]
71900414 1 12 System.Collections.Generic.ObjectEqualityComparer`1[[System.Type, mscorlib]]
718fde9c 1 16 System.Security.Policy.AssemblyEvidenceFactory
7190be18 1 20 System.IO.Stream+NullStream
71901888 1 20 Microsoft.Win32.SafeHandles.SafeFileHandle
718fdde8 1 20 Microsoft.Win32.SafeHandles.SafePEFileHandle
7190c3dc 1 24 System.IO.TextWriter+SyncTextWriter
71902298 1 24 System.Version
71900994 2 24 System.Int32
71461e00 1 24 System.Collections.Generic.List`1[[System.String, mscorlib]]
7190c2e4 1 28 System.IO.__ConsoleStream
7190c29c 1 28 Microsoft.Win32.Win32Native+InputRecord
...[omitted for brevity]...
71900958 6 452 System.Int32[]
718fff54 22 616 System.RuntimeType
718ff54c 6 626 System.Char[]
7190316c 1 783 System.Byte[]
71901e50 3 924 System.Globalization.CultureData
718fef34 4 17604 System.Object[]
718ff698 19 524868 System.String[]
00f2b548 24 525636 Free
718feb40 100154 8604850 System.String
Total 100299 objects
The instances of "System.String" are 100,154, but you can't find the root cause why string was being leaked. In this case, just run RefOwner32/RefOwner64 on the dump file as follows,
c:\temp\RefOwner\bin> RefOwner32.exe c:\tmp\ConsoleApp1.dmp System.String
Found CLR Version: v4.7.3260.00
Filesize: 6EF000
Timestamp: 5BB7BCB7
Dac File: mscordacwks_X86_X86_4.7.3260.00.dll
Local dac location: C:\Windows\Microsoft.NET\Framework\v4.0.30319\mscordacwks.dll
System.String, # of instances: 100034
1 System.AppDomainSetup(1)
31 System.Object[](3)
100003 System.String[](2)
Total: 100035
Two System.String[] instances make references onto 100,034 System.String instances. And "/d" switch will show more information.
c:\temp\RefOwner\bin> RefOwner32.exe /d c:\tmp\ConsoleApp1.dmp System.String
...[생략]...
System.String, # of instances: 100034
System.String, # of instances: 100034
1 System.AppDomainSetup(1)
[2b714e0, 1]
31 System.Object[](3)
[3b71020, 1]
[3b72300, 2]
[3b72520, 28]
100003 System.String[](2)
[2b7156c, 3]
[3bd5570, 100000]
Total: 100035
That's it. Because of 0x3bd5570 object, 100,000 of System.String objects couldn't be collected. Again with 3bd5570 address, RefOwner show the owner of System.String[].
c:\temp\RefOwner\bin\x86> RefOwner32.exe /d c:\tmp\ConsoleApp1.dmp 3bd5570
Found CLR Version: v4.7.3260.00
Filesize: 6EF000
Timestamp: 5BB7BCB7
Dac File: mscordacwks_X86_X86_4.7.3260.00.dll
Local dac location: C:\Windows\Microsoft.NET\Framework\v4.0.30319\mscordacwks.dll
3bd5570, # of instances: 1
1 System.Collections.Generic.List<System.String>(1)
[2b720a4, 1]
Total: 1
Or, at this stage, you can find the GC root with "!gcroot 3bd5570" in windbg.
If you need some features or whatever, make an issue at https://github.com/stjeong/RefOwner/issues
Any help and advices for this repo are welcome.
Apache License V2.0
(Refer to LICENSE.txt)