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[RadixTree][7/N Refactor]: Refactor mamba radix tree, release dup kvcache in insert func#19429

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ispobock merged 3 commits intosgl-project:mainfrom
hzh0425:hybrid/mamba-release
Mar 13, 2026
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[RadixTree][7/N Refactor]: Refactor mamba radix tree, release dup kvcache in insert func#19429
ispobock merged 3 commits intosgl-project:mainfrom
hzh0425:hybrid/mamba-release

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@hzh0425 hzh0425 commented Feb 26, 2026

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python3 test/registered/4-gpu-models/test_qwen3_next_models.py

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@hzh0425 hzh0425 added the run-ci label Feb 26, 2026
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Summary of Changes

Hello @hzh0425, 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 refactors the Mamba Radix Tree's memory management to enhance efficiency by intelligently handling duplicate KV cache entries. By introducing a prev_prefix_len parameter, the system can now precisely determine which parts of the KV cache to release during insertion, thereby optimizing memory usage and preventing redundant allocations. The changes are supported by new unit tests to ensure correctness and robustness.

Highlights

  • Optimized KV Cache Management: Introduced a prev_prefix_len parameter to the insert and _insert_helper functions in the Mamba Radix Tree, enabling more granular control over KV cache freeing during insertion.
  • Reduced Duplicate KV Cache Allocation: Implemented logic to conditionally free duplicate KV cache entries based on prev_prefix_len, preventing unnecessary memory allocation for shared prefixes.
  • Refactored Cache Freeing Logic: Removed redundant KV cache freeing calls from cache_finished_req and _skip_cache_unfinished_req methods, centralizing the freeing logic within _insert_helper.
  • Comprehensive Unit Testing: Added a new unit test, test_insert_prev_prefix_len, to thoroughly validate the new KV cache freeing mechanism under various scenarios, including full, partial, and no freeing.

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Changelog
  • python/sglang/srt/mem_cache/mamba_radix_cache.py
    • Modified insert method to accept prev_prefix_len in InsertParams.
    • Updated _insert_helper signature to include prev_prefix_len with a default value.
    • Implemented conditional freeing of KV cache entries within _insert_helper based on prev_prefix_len and total_prefix_length.
    • Removed unconditional token_to_kv_pool_allocator.free calls from cache_finished_req and _skip_cache_unfinished_req.
  • test/registered/radix_cache/test_mamba_unittest.py
    • Added a new helper method _setup_tree_and_allocator to streamline test environment setup for MambaRadixCache.
    • Introduced test_insert_prev_prefix_len to verify the correct behavior of KV cache freeing with different prev_prefix_len values during insertion.
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  • The pull request was created by hzh0425.
  • No human activity (comments, reviews) has been recorded on this pull request yet.
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@hzh0425 hzh0425 changed the title [RadixTree][6/N Refactor]: Refactor mamba radix tree, release dup kvcache in insert func [RadixTree][7/N Refactor]: Refactor mamba radix tree, release dup kvcache in insert func Feb 26, 2026
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Code Review

This pull request refactors the Mamba radix tree to correctly release duplicate KV cache entries during insertion. The core logic is moved into the _insert_helper function, which now accepts a prev_prefix_len parameter to protect a certain prefix length from being freed. This is a good refactoring that centralizes the logic and improves correctness. The accompanying new test, test_insert_prev_prefix_len, is comprehensive and validates the new behavior under various scenarios.

My main feedback is regarding code duplication in the test file. The new test helper _setup_tree_and_allocator duplicates a significant amount of setup code from an existing test. This could be improved for better maintainability.

Comment thread test/registered/radix_cache/test_mamba_unittest.py
@hzh0425
optimize code
4c29525
@hzh0425
Merge remote-tracking branch 'origin/main' into hybrid/mamba-release
44d6fbb 
# Conflicts:
#	python/sglang/srt/mem_cache/mamba_radix_cache.py
@ispobock ispobock mentioned this pull request Mar 12, 2026
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@ispobock ispobock merged commit 197f807 into sgl-project:main Mar 13, 2026
411 of 458 checks passed
liubiyongge pushed a commit to liubiyongge/sglang that referenced this pull request Mar 13, 2026
@hzh0425 @liubiyongge
[RadixTree][7/N Refactor]: Refactor mamba radix tree, release dup kvc…
98def4e 
…ache in insert func (sgl-project#19429)
@ziruiliu ziruiliu mentioned this pull request Mar 13, 2026
Merged
5 tasks
yhyang201 pushed a commit to yhyang201/sglang that referenced this pull request Mar 15, 2026
@hzh0425 @yhyang201
[RadixTree][7/N Refactor]: Refactor mamba radix tree, release dup kvc…
8e49d26 
…ache in insert func (sgl-project#19429)
Wangzheee pushed a commit to Wangzheee/sglang that referenced this pull request Mar 21, 2026
@hzh0425 @Wangzheee
[RadixTree][7/N Refactor]: Refactor mamba radix tree, release dup kvc…
78391f7 
…ache in insert func (sgl-project#19429)
0-693 pushed a commit to 0-693/sglang that referenced this pull request Mar 25, 2026
@hzh0425 @0-693
[RadixTree][7/N Refactor]: Refactor mamba radix tree, release dup kvc…
0dda9ef 
…ache in insert func (sgl-project#19429)
JustinTong0323 pushed a commit to JustinTong0323/sglang that referenced this pull request Apr 7, 2026
@hzh0425
[RadixTree][7/N Refactor]: Refactor mamba radix tree, release dup kvc…
1053906 
…ache in insert func (sgl-project#19429)
yhyang201 pushed a commit to yhyang201/sglang that referenced this pull request Apr 22, 2026
@hzh0425
[RadixTree][7/N Refactor]: Refactor mamba radix tree, release dup kvc…
091cef5 
…ache in insert func (sgl-project#19429)
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@ispobock ispobock ispobock approved these changes

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