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Fix missing clone in hicache#20130

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ispobock merged 1 commit intomainfrom
fix-missing-clone
Mar 8, 2026
Merged

Fix missing clone in hicache#20130
ispobock merged 1 commit intomainfrom
fix-missing-clone

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@ispobock ispobock commented Mar 8, 2026

Motivation

follow up: #17400

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gemini-code-assist Bot commented Mar 8, 2026

Summary of Changes

Hello, 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 resolves a critical issue within the hiradix_cache module where tensor assignments were creating references instead of independent copies. By introducing explicit .clone() calls, the change guarantees that cache nodes hold their own distinct data, thereby preventing unexpected modifications when the original tensor data changes. This enhancement improves the robustness and reliability of the caching mechanism, especially in complex scenarios like KV cache recomputation.

Highlights

  • Data Integrity: Ensured that tensor values assigned to cache nodes are explicitly cloned, preventing unintended shared references and potential data corruption.
  • Cache Consistency: Addressed a subtle bug in the hiradix_cache module related to how tensor slices were handled during load_back and insert operations, particularly for evicted nodes and KV cache recomputation.

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Changelog
  • python/sglang/srt/mem_cache/hiradix_cache.py
    • Added .clone() to the assignment of node.value in the load_back function to ensure a deep copy of device indices.
    • Added .clone() to the assignment of node.value in the insert function when handling evicted nodes to prevent shared references.
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ispobock commented Mar 8, 2026

/tag-and-rerun-ci

@github-actions github-actions Bot added the run-ci label Mar 8, 2026
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Code Review

This pull request adds .clone() calls during tensor assignments in python/sglang/srt/mem_cache/hiradix_cache.py. Specifically, in the load_back function, slices of device_indices are cloned, and in the insert function, slices of the value tensor are cloned when updating evicted nodes. This ensures that each node.value becomes an independent tensor with its own memory, rather than a view into a shared underlying storage. This change prevents potential memory corruption issues and aligns with the memory management strategy seen elsewhere in the cache logic, such as in the _split_node function.

@ispobock ispobock merged commit 07359ef into main Mar 8, 2026
155 of 174 checks passed
@ispobock ispobock deleted the fix-missing-clone branch March 8, 2026 15:21
liubiyongge pushed a commit to liubiyongge/sglang that referenced this pull request Mar 13, 2026
@ispobock @liubiyongge
Fix missing clone in hicache (sgl-project#20130)
1c0c979
Wangzheee pushed a commit to Wangzheee/sglang that referenced this pull request Mar 21, 2026
@ispobock @Wangzheee
Fix missing clone in hicache (sgl-project#20130)
678e15f
JustinTong0323 pushed a commit to JustinTong0323/sglang that referenced this pull request Apr 7, 2026
@ispobock
Fix missing clone in hicache (sgl-project#20130)
1994112
yhyang201 pushed a commit to yhyang201/sglang that referenced this pull request Apr 22, 2026
@ispobock
Fix missing clone in hicache (sgl-project#20130)
d5035b6
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@yizhang2077 yizhang2077 yizhang2077 approved these changes

@merrymercy merrymercy Awaiting requested review from merrymercy merrymercy is a code owner

@Ying1123 Ying1123 Awaiting requested review from Ying1123 Ying1123 is a code owner

@hnyls2002 hnyls2002 Awaiting requested review from hnyls2002 hnyls2002 is a code owner

@xiezhq-hermann xiezhq-hermann Awaiting requested review from xiezhq-hermann xiezhq-hermann is a code owner

@hanming-lu hanming-lu Awaiting requested review from hanming-lu hanming-lu is a code owner

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