[Json] Avoid ReadOnlySequence with Stream deserializing #118408
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BrennanConroy
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PranavSenthilnathan,
Copilot and
eiriktsarpalis
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Pull Request Overview
This PR optimizes JSON deserialization from streams by eliminating redundant ReadOnlySequence creation and conditional checks when constructing Utf8JsonReader instances. The change aims to address performance regressions noted in issue #118173.
Key changes:
- Refactors reader creation logic into specialized methods on buffer state classes
- Eliminates duplicate conditional logic for single vs multi-segment sequences
- Simplifies the deserialization path by centralizing reader instantiation
Reviewed Changes
Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
| IReadBufferState.cs | Adds abstract GetReader method to the interface |
| StreamReadBufferState.cs | Implements GetReader for stream-based buffering |
| PipeReadBufferState.cs | Implements GetReader with single/multi-segment optimization |
| JsonTypeInfoOfT.ReadHelper.cs | Replaces inline reader creation with GetReader call |
src/libraries/System.Text.Json/src/System/Text/Json/Serialization/IReadBufferState.cs
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Tagging subscribers to this area: @dotnet/area-system-text-json, @gregsdennis |
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@EgorBot -windows_intel --filter "*System.Text.Json.Serialization.Tests.ReadJson<*FromStream" |
eiriktsarpalis
approved these changes
Aug 6, 2025
src/libraries/System.Text.Json/src/System/Text/Json/Serialization/IReadBufferState.cs
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This was referenced Aug 11, 2025
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Removes the construction of a
ReadOnlySequenceandifchecks for creating aUtf8JsonReaderin theStreamcase. Might fix the regressions shown in #118173 (comment).I say might because locally running the microbenchmarks didn't give the most consistent results, but over a bunch of runs the general trend was that this change improved things.