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[Schedule] bug fix for schedule enhancer#15834

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iforgetmyname merged 1 commit intosgl-project:ifmn/eagle-dp-attnfrom
iforgetmyname:ifmn/bug_fix_lp
Dec 25, 2025
Merged

[Schedule] bug fix for schedule enhancer#15834
iforgetmyname merged 1 commit intosgl-project:ifmn/eagle-dp-attnfrom
iforgetmyname:ifmn/bug_fix_lp

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@liupeng374
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Motivation

Modifications

Accuracy Tests

Benchmarking and Profiling

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Summary of Changes

Hello @liupeng374, 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 addresses a bug within the SchedulerEnhancer component by modifying a key threshold. The change is designed to refine the conditions under which a specific scheduling strategy is maintained when the system is experiencing high load, ultimately enhancing the scheduler's overall stability and responsiveness.

Highlights

  • Scheduler Bug Fix: The max_stable_count parameter in the SchedulerEnhancer class has been increased from 30 to 200. This adjustment aims to prevent the prefill-prioritized scheduling strategy from persisting too long when data processing units are at full load, thereby improving scheduling behavior and stability.

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Code Review

This pull request addresses a bug in the scheduler enhancer by increasing the max_stable_count from 30 to 200. This change makes the scheduler wait longer before allowing new prefill requests when there is a load imbalance across data parallel units, thus prioritizing decode operations for a longer period to help stabilize the load. My review focuses on improving the maintainability of this change. I've suggested making the new threshold value a named constant to avoid magic numbers and improving the clarity of the associated comment.

Comment on lines +18 to +19
# If scheduling is performed 200 times and some dp units are still at full load, the prefill-prioritized scheduling strategy will still be used.
self.max_stable_count = 200
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medium

The value 200 is a magic number, which can make the code harder to understand and maintain. It would be better to define it as a named constant at the top of the file, for example: _MAX_STABLE_COUNT = 200. In the long term, making this a configurable server argument would provide more flexibility.

Additionally, the comment on line 18 could be clearer. The current logic blocks prefill when there's load imbalance and allows it again after max_stable_count cycles to prevent starvation. A more descriptive comment would be helpful.

Suggested change
# If scheduling is performed 200 times and some dp units are still at full load, the prefill-prioritized scheduling strategy will still be used.
self.max_stable_count = 200
# If load imbalance persists for `max_stable_count` cycles, prefill is allowed again to prevent starvation.
self.max_stable_count = 200

@iforgetmyname iforgetmyname merged commit 92fe108 into sgl-project:ifmn/eagle-dp-attn Dec 25, 2025
1 check passed
@iforgetmyname iforgetmyname deleted the ifmn/bug_fix_lp branch December 25, 2025 14:59
Liwansi added a commit to iforgetmyname/sglang that referenced this pull request Dec 29, 2025
…glang into eagle-sche

* 'ifmn/eagle-dp-attn' of https://github.com/sgl-project/sglang: (22 commits)
  dp scheduler enhance support with chunked prefill (sgl-project#16071)
  modify suffix decoding
  CI dependency update (sgl-project#16063)
  fix rotary_embedding init npu (sgl-project#16011)
  feat: bugfix and accuracy fix for stablelm2_1_6b (sgl-project#15932)
  Update model and feature support for Ascend NPU (sgl-project#16005)
  Bugfix for Llama4 (sgl-project#15929)
  Bugfix for ds-vl2 (sgl-project#15894)
  gme qwen vl runners fix (sgl-project#15899)
  add profiling in scheduler (sgl-project#15876)
  llama use triton rope op (sgl-project#15855)
  suffix decoding adapt npu
  suffix decoding adapt npu
  Add suffix decoding speculative algorithm from feature 13553
  cherry sgl-project#15434: qwen3 vl performance update
  cherry sgl-project#15597: fix Qwen3-VL-30B-A3B-Instruct accuracy loss
  [Schedule] bug fix for schedule enhancer (sgl-project#15834)
  minilb support roundrobin (sgl-project#15824)
  fix torchair compile issue
  cherry sgl-project#15187: lora fix
  ...

# Conflicts:
#	python/sglang/srt/managers/scheduler.py
#	python/sglang/srt/managers/scheduler_enhancer.py
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2 participants