一：背景
1. 讲故事
微信里有一位朋友找到我，说他们公司的程序存在内存暴涨问题，自己分析了下没有找到原因，让我看下怎么回事？由于大家都有dump分析基础，所以交流互通上还是很顺利的，接下来就是上dump分析啦。
二：内存暴涨分析
1. 为什么会内存暴涨
先还是老套路，用 !address -summary 观察下内存分布情况，输出如下：- 0:000> !address -summary
- --- Usage Summary ---------------- RgnCount ----------- Total Size -------- %ofBusy %ofTotal
- Free 363 7dfd`e87c7000 ( 125.992 TB) 98.43%
- <unknown> 9276 201`e5858000 ( 2.007 TB) 99.96% 1.57%
- Heap 65 0`2547f000 ( 596.496 MB) 0.03% 0.00%
- Image 1855 0`09d35000 ( 157.207 MB) 0.01% 0.00%
- Stack 93 0`02c00000 ( 44.000 MB) 0.00% 0.00%
- Other 9 0`001de000 ( 1.867 MB) 0.00% 0.00%
- TEB 31 0`0003e000 ( 248.000 kB) 0.00% 0.00%
- PEB 1 0`00001000 ( 4.000 kB) 0.00% 0.00%
- --- State Summary ---------------- RgnCount ----------- Total Size -------- %ofBusy %ofTotal
- MEM_FREE 363 7dfd`e87c7000 ( 125.992 TB) 98.43%
- MEM_RESERVE 690 201`2b6d4000 ( 2.005 TB) 99.82% 1.57%
- MEM_COMMIT 10640 0`ec155000 ( 3.689 GB) 0.18% 0.00%
- 0:000> !dumpheap -stat
- Statistics:
- MT Count TotalSize Class Name
- ...
- 0179c7715cb0 1,847,901 451,265,880 Free
- 7ffc6e0a2888 2 536,870,960 System.WeakReference<Microsoft.Extensions.DependencyInjection.ServiceProvider>[]
- 7ffc6e0a2260 60,873,978 1,460,975,472 System.WeakReference<Microsoft.Extensions.DependencyInjection.ServiceProvider>
- Total 63,333,893 objects, 2,494,520,292 bytes
- 0:000> !dumpheap -mt 7ffc6e0a2260
- Address MT Size
- 017988001000 7ffc6e0a2260 24
- 017988001018 7ffc6e0a2260 24
- 017988001030 7ffc6e0a2260 24
- 017988001048 7ffc6e0a2260 24
- 017988001060 7ffc6e0a2260 24
- 017988001078 7ffc6e0a2260 24
- 017988001090 7ffc6e0a2260 24
- 0179880010a8 7ffc6e0a2260 24
- ...
- 017a405f1020 7ffc6e0a2260 24
- 0:000> !gcroot 0179880010a8
- Caching GC roots, this may take a while.
- Subsequent runs of this command will be faster.
- 0:000> !dumpobj /d 17a405f1020
- Name: System.WeakReference`1[[Microsoft.Extensions.DependencyInjection.ServiceProvider, Microsoft.Extensions.DependencyInjection]][]
- MethodTable: 00007ffc6e0a2888
- EEClass: 00007ffc6dbeb4f8
- Tracked Type: false
- Size: 536870936(0x20000018) bytes
- Array: Rank 1, Number of elements 67108864, Type CLASS (Print Array)
- Fields:
- None
- 0:000> s-q 0 L?0xffffffffffffffff 17a405f1020
- 00000179`c95861d0 0000017a`405f1020 03a0dcfa`03a0dcfa
- 0:000> !lno 0000017a`405f1020
- Before: 017a405f1000 32 (0x20) Free
- Current: 017a405f1020 24 (0x18) System.WeakReference<Microsoft.Extensions.DependencyInjection.ServiceProvider>[]
- Error Detected: Object 17a405f1020 has a bad member at offset 12054c00: ??? [verify heap]
- Could not find object after 17a405f1020
- Heap local consistency not confirmed.
- 0:000> !lno 00000179`c95861d0
- Before: 0179c95861c8 32 (0x20) System.Collections.Generic.List<System.WeakReference<Microsoft.Extensions.DependencyInjection.ServiceProvider>>
- Next: 0179c95861e8 24 (0x18) System.WeakReference<Microsoft.Extensions.DependencyInjection.ServiceProvider>[]
- Heap local consistency confirmed.
- 0:000> !dumpobj /d 179c95861c8
- Name: System.Collections.Generic.List`1[[System.WeakReference`1[[Microsoft.Extensions.DependencyInjection.ServiceProvider, Microsoft.Extensions.DependencyInjection]], System.Private.CoreLib]]
- MethodTable: 00007ffc6e0a2340
- EEClass: 00007ffc6dce0000
- Tracked Type: false
- Size: 32(0x20) bytes
- File: D:\xxx\A_api\System.Private.CoreLib.dll
- Fields:
- MT Field Offset Type VT Attr Value Name
- 00007ffc6de328f0 400209f 8 System.__Canon[] 0 instance 0000017a405f1020 _items
- 00007ffc6dc894b0 40020a0 10 System.Int32 1 instance 60873978 _size
- 00007ffc6dc894b0 40020a1 14 System.Int32 1 instance 60873978 _version
- 00007ffc6de328f0 40020a2 8 System.__Canon[] 0 static dynamic statics NYI s_emptyArray
- 0:000> s-q 0 L?0xffffffffffffffff 179c95861c8
- 00000179`c77571d8 00000179`c95861c8 00000000`00000000
- 00000179`c95861b8 00000179`c95861c8 0800004e`00000000
- 0:000> !lno 00000179`c77571d8
- Failed to find the segment of the managed heap where the object 179c77571d8 resides
- 0:000> !lno 00000179`c95861b8
- Before: 0179c9586108 192 (0xc0) Microsoft.Extensions.DependencyInjection.DependencyInjectionEventSource
- Next: 0179c95861c8 32 (0x20) System.Collections.Generic.List<System.WeakReference<Microsoft.Extensions.DependencyInjection.ServiceProvider>>
- Heap local consistency confirmed.
根据卦中的图和输出，终于找到了原来是 DependencyInjectionEventSource._providers 承担了所有，接下来的关注点就来到了 DependencyInjectionEventSource。
2. xxxEventSource 是什么
从名字上看和 ETW 事件有关，接下来用 !eeversion 观察 .net 版本，寻找其对应的C#源代码。- 0:000> !eeversion
- 6.0.3624.51421 free
- 6,0,3624,51421 @Commit: f1dd57165bfd91875761329ac3a8b17f6606ad18
- Workstation mode
- SOS Version: 9.0.13.2701 retail build
从上面的源代码看，其实也看不出来个所以，毕竟底层的架构我不熟悉，本着我不是第一个吃螃蟹的人，所以拿关键词在网上索一下，果然 stephentoub 大佬在去年4月份就发现了这个问题，在 .net10 中做了修复，看描述是一个优化级的bug，官方链接：https://github.com/dotnet/runtime/issues/114599 截图如下：
修改后的代码如下，果然加了很多的业务逻辑来处理。- [NonEvent]
- public void ServiceProviderBuilt(ServiceProvider provider)
- {
- lock (_providers)
- {
- int providersCount = _providers.Count;
- if (providersCount > 0 &&
- (_survivingProvidersCount is int spc ? (uint)providersCount >= 2 * (uint)spc : providersCount == _providers.Capacity))
- {
- _providers.RemoveAll(static p => !p.TryGetTarget(out _));
- _survivingProvidersCount = _providers.Count;
- }
- _providers.Add(new WeakReference<ServiceProvider>(provider));
- }
- WriteServiceProviderBuilt(provider);
- }
解决办法很简单，两种方式：
- 检查代码里写 BuildServiceProvider 的地方没有即时的 Dispose。
- 升级到 .NET10 ，这是最简单粗暴的方法。
把结论告诉朋友后，朋友终于在2天后给我反馈了好消息，好心情溢于言表！
三：总结
dump之旅是一个修理工不断自我修炼的过程，必须学会在绝望中寻找希望的能力。
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