升级至 .NET 7 之后 System.Text.Json 在序列化大文本时会出现 OutOfMemoryException
0
悬赏园豆：30
[待解决问题]
在升级至 .NET 7 之后，已经在2个项目中遇到 System.Text.Json 在序列化大文本时会出现 OutOfMemoryException，序列化的对象中保存了博文内容，当博文内容字符数过多时就容易引发这个异常
以下是异常日志
System.OutOfMemoryException: Exception of type 'System.OutOfMemoryException' was thrown.
at System.GC.AllocateNewArray(IntPtr typeHandle, Int32 length, GC_ALLOC_FLAGS flags)
at System.GC.<AllocateUninitializedArray>g__AllocateNewUninitializedArray|66_0[T](Int32 length, Boolean pinned)
at System.Buffers.TlsOverPerCoreLockedStacksArrayPool`1.Rent(Int32 minimumLength)
at System.Text.Json.Utf8JsonWriter.WriteStringEscapeValue(ReadOnlySpan`1 value, Int32 firstEscapeIndexVal)
at System.Text.Json.Serialization.JsonConverter`1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
at System.Text.Json.Serialization.Metadata.JsonPropertyInfo`1.GetMemberAndWriteJson(Object obj, WriteStack& state, Utf8JsonWriter writer)
at System.Text.Json.Serialization.Converters.ObjectDefaultConverter`1.OnTryWrite(Utf8JsonWriter writer, T value, JsonSerializerOptions options, WriteStack& state)
at System.Text.Json.Serialization.JsonConverter`1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
at System.Text.Json.Serialization.Converters.ListOfTConverter`2.OnWriteResume(Utf8JsonWriter writer, TCollection value, JsonSerializerOptions options, WriteStack& state)
at System.Text.Json.Serialization.JsonCollectionConverter`2.OnTryWrite(Utf8JsonWriter writer, TCollection value, JsonSerializerOptions options, WriteStack& state)
at System.Text.Json.Serialization.JsonConverter`1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
at System.Text.Json.Serialization.JsonConverter`1.WriteCore(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
at System.Text.Json.Serialization.JsonConverter`1.WriteCoreAsObject(Utf8JsonWriter writer, Object value, JsonSerializerOptions options, WriteStack& state)
at System.Text.Json.JsonSerializer.WriteCore[TValue](Utf8JsonWriter writer, TValue& value, JsonTypeInfo jsonTypeInfo, WriteStack& state)
at System.Text.Json.JsonSerializer.WriteStreamAsync[TValue](Stream utf8Json, TValue value, JsonTypeInfo jsonTypeInfo, CancellationToken cancellationToken)
at System.Text.Json.JsonSerializer.WriteStreamAsync[TValue](Stream utf8Json, TValue value, JsonTypeInfo jsonTypeInfo, CancellationToken cancellationToken)
at System.Text.Json.JsonSerializer.WriteStreamAsync[TValue](Stream utf8Json, TValue value, JsonTypeInfo jsonTypeInfo, CancellationToken cancellationToken)
Microsoft.AspNetCore.Mvc.Formatters.SystemTextJsonOutputFormatter.WriteResponseBodyAsync(OutputFormatterWriteContext context, Encoding selectedEncoding)
问题补充：
从 System.Text.Json.Utf8JsonWriter 对应的实现代码 WriteStringEscapeValue 看，异常是在下面的代码中执行 ArrayPool<char>.Shared.Rent 时抛出的
Span<char> escapedValue = length <= JsonConstants.StackallocCharThreshold ?
stackalloc char[JsonConstants.StackallocCharThreshold] :
(valueArray = ArrayPool<char>.Shared.Rent(length));
ASP.NET Core 中对应的源码 SystemTextJsonOutputFormatter.cs#L82
await JsonSerializer.SerializeAsync(responseStream, context.Object, objectType, SerializerOptions, httpContext.RequestAborted);
所有回答(2)
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GC提示内存不足，或许可以尝试调整垃圾回收器的设置；
https://learn.microsoft.com/zh-cn/dotnet/core/runtime-config/garbage-collector
0
是 .NET 7 GC 的问题引起的
in .NET 7 we have enabled new Regions functionality within the GC. Here are the details: #43844. Since this was a foundational change, we also shipped a separate GC which keeps the previous "Segments" functionality -- in case there are some issues like this one.
1月会发布更新，目前的临时解决方法是添加环境变量 COMPlus_GCName=libclrgc.so(linux) 或者 COMPlus_GCName=clrgc.dll(windows)
.NET 7.0.3 今天发布了，这个问题在 Fix spurious OOMs after upgrading to 7 中修复了
.NET 7.0.3 没有彻底解决问题，还是会出现 OutOfMemoryException
github 上的相关 issue https://github.com/dotnet/runtime/issues/66102
– dudu 1年前System.Text.Json.Utf8JsonWriter 对应的实现代码 WriteStringEscapeValue
– dudu 1年前github 上的相关 issue Multiple 'System.OutOfMemoryException' errors in .NET 7
– dudu 1年前