Reduce overhead from using AutomaticDecompression#122676
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MihaZupan merged 3 commits intodotnet:mainfrom Jan 7, 2026
Merged
Reduce overhead from using AutomaticDecompression#122676MihaZupan merged 3 commits intodotnet:mainfrom
MihaZupan merged 3 commits intodotnet:mainfrom
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Pull request overview
This PR aims to reduce memory allocations when using AutomaticDecompression in SocketsHttpHandler through three main optimizations:
- Fast-path optimization for the Accept-Encoding header when it hasn't been set yet
- Using
TryGetValuesto avoid collection allocation when checking for Content-Encoding headers - Moving content headers instead of copying them when creating decompressed content wrappers
Key Changes
- Optimized Accept-Encoding header handling with a pre-computed header value string
- Changed Content-Encoding check to use
TryGetValuesand work directly with the returned string array - Modified decompressed content constructors to accept and use the encoding array for header manipulation
Reviewed changes
Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.
| File | Description |
|---|---|
| SocketsHttpHandler.cs | Added defensive check to filter unsupported decompression methods and added constant for supported methods |
| DecompressionHandler.cs | Implemented fast-path for Accept-Encoding header, optimized Content-Encoding check, modified header handling in decompressed content classes |
| HttpContent.cs | Added SetHeaders method to support moving headers between content objects |
src/libraries/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/DecompressionHandler.cs
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src/libraries/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/DecompressionHandler.cs
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This was referenced Jan 9, 2026
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AutomaticDecompression, theAccept-Encodingheader is practically never touched manually by the user. We can check for this very common case when the header isn't set yet and just add the one value representing all supported methods without more validation.HttpHeaderValueCollection, the backingList<object>,HeaderStoreItemInfoand enumerators when walking through existing values.TryGetValuesto avoid the collection allocation if there is noContent-Encodingheader.Simple in-memory benchmark (no real IO)