Add doc for qwen3 next

[yizhang2077]

Motivation

Modifications

Accuracy Tests

Benchmarking and Profiling

Checklist

• Format your code according to the Format code with pre-commit.
• Add unit tests according to the Run and add unit tests.
• Update documentation according to Write documentations.
• Provide accuracy and speed benchmark results according to Test the accuracy and Benchmark the speed.
• Follow the SGLang code style guidance.
• Work with maintainers to merge your PR. See the PR Merge Process

[gemini-code-assist]

Summary of Changes

Hello @yizhang2077, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances the documentation for Qwen3-Next models by providing crucial information on a new memory configuration parameter and introducing the MambaRadixCache feature. These updates aim to equip users with the knowledge to optimize memory allocation and leverage advanced caching strategies, ultimately improving the inference performance and flexibility of Qwen3-Next models within SGLang.

Highlights

• New Configuration Option: Added documentation for the --mamba-full-memory-ratio configuration option, which controls the ratio of mamba state memory to full KV cache memory for Qwen3-Next models.
• Mamba Radix Cache Documentation: Introduced a new section detailing MambaRadixCache for Qwen3-Next models, explaining its purpose in improving inference speed through prefix caching.
• Mamba Radix Cache Versions: Documented two versions of MambaRadixCache: V1 (default, closes overlap schedule for compatibility) and V2 (optimized, compatible with page size > 1, overlap schedule, speculative decoding, and supports branching positions, requiring the extra_buffer strategy).

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[gemini-code-assist]

Code Review

This pull request adds documentation for new features related to Qwen3-Next models, specifically the --mamba-full-memory-ratio argument and details about MambaRadixCache. The new documentation is helpful, but I've found a few typos and a potentially misleading statement about feature compatibility that could be clarified. My review includes suggestions to correct these for better accuracy and readability.