[Models] Optimize DeepSeek V3 MLA projection layout

[chang-wenbin]

Motivation

Optimize DeepSeek V3 MLA K_b/V_b projection layout handling and reduce intermediate transpose/padding work in the attention forward path.

Modifications

• Added KVBatchLinear.forward_k_b_thd() for token-head-dim K_b projection.
• Added KVBatchLinear.forward_v_b_htr() for token-head-rank V_b projection.
• Updated DeepSeek V3 MLA, sliding-window MLA, and DSA attention paths to use the new helpers.
• Removed prefill value padding/slicing so the value path keeps v_head_dim directly.

Usage or Command

N/A

Accuracy Tests

N/A. This PR changes DeepSeek V3 attention forward/output shape handling, but no accuracy or logits-alignment result is provided yet.

Checklist

• Add at least a tag in the PR title.
  • Tag list: [[FDConfig],[APIServer],[Engine], [Scheduler], [PD Disaggregation], [Executor], [Graph Optimization], [Speculative Decoding], [RL], [Models], [Quantization], [Loader], [OP], [KVCache], [DataProcessor], [BugFix], [Docs], [CI], [Optimization], [Feature], [Benchmark], [Others], [XPU], [HPU], [GCU], [DCU], [Iluvatar], [Metax]]
  • You can add new tags based on the PR content, but the semantics must be clear.
• Format your code, run pre-commit before commit.
• Add unit tests. Please write the reason in this PR if no unit tests.
• Provide accuracy results.
• If the current PR is submitting to the release branch, make sure the PR has been submitted to the develop branch, then cherry-pick it to the release branch with the [Cherry-Pick] PR tag.

[PaddlePaddle-bot]

🤖 Paddle-CI-Agent | pr_review | 2026-06-29 00:03:12

📋 Review 摘要

PR 概述：调整 DeepSeek V3/DeepSeek V3.2 MLA 路径中的 K_b/V_b 投影布局处理，减少 transpose + bmm + transpose 形式的中间变换，并移除 prefill value padding/slice。

变更范围：fastdeploy/model_executor/layers/linear.py、fastdeploy/model_executor/models/deepseek_v3.py

影响面 Tag：[Models] [OP]

问题

未发现阻塞性问题。PR 规范问题在下面章节报,不要在这里重复

📝 PR 规范检查

当前 PR 标题缺少官方 Tag，PR 描述保留了模板但 Motivation、Modifications、Usage or Command、Accuracy Tests 均为空；本次改动触及模型 forward/attention 输出形状路径，也未提供精度或 logits 对齐结果。建议按下面内容补齐。

标题建议（可直接复制）：

• [Models] Optimize DeepSeek V3 MLA projection layout

PR 描述建议（点击展开，可直接复制）

## Motivation
Optimize DeepSeek V3 MLA K_b/V_b projection layout handling and reduce intermediate transpose/padding work in the attention forward path.

## Modifications
- Added `KVBatchLinear.forward_k_b_thd()` for token-head-dim K_b projection.
- Added `KVBatchLinear.forward_v_b_htr()` for token-head-rank V_b projection.
- Updated DeepSeek V3 MLA, sliding-window MLA, and DSA attention paths to use the new helpers.
- Removed prefill value padding/slicing so the value path keeps `v_head_dim` directly.

## Usage or Command
N/A

## Accuracy Tests
N/A. This PR changes DeepSeek V3 attention forward/output shape handling, but no accuracy or logits-alignment result is provided yet.

## Checklist

- [x] Add at least a tag in the PR title.
  - Tag list: [`[FDConfig]`,`[APIServer]`,`[Engine]`, `[Scheduler]`, `[PD Disaggregation]`, `[Executor]`, `[Graph Optimization]`, `[Speculative Decoding]`, `[RL]`, `[Models]`, `[Quantization]`, `[Loader]`, `[OP]`, `[KVCache]`, `[DataProcessor]`, `[BugFix]`, `[Docs]`, `[CI]`, `[Optimization]`, `[Feature]`, `[Benchmark]`, `[Others]`, `[XPU]`, `[HPU]`, `[GCU]`, `[DCU]`, `[Iluvatar]`, `[Metax]`]
  - You can add new tags based on the PR content, but the semantics must be clear.
- [ ] Format your code, run `pre-commit` before commit.
- [ ] Add unit tests. Please write the reason in this PR if no unit tests.
- [ ] Provide accuracy results.
- [ ] If the current PR is submitting to the `release` branch, make sure the PR has been submitted to the `develop` branch, then cherry-pick it to the `release` branch with the `[Cherry-Pick]` PR tag.

总体评价

本轮按风险优先审查了 KVBatchLinear 新增投影 helper，以及 DeepSeek V3 MLA/DSA/sliding-window 路径中 K/V 维度、latent rank 和 merge 输出的形状链路。代码层面暂未确认到需要阻塞合入的问题；但该 PR 修改模型 forward 热路径，建议补充至少一组 DeepSeek V3/DeepSeek V3.2 logits 或精度对齐结果，并说明是否覆盖 prefill、decode、mixed、DSA/滑窗路径。

[codecov-commenter]

Codecov Report

❌ Patch coverage is 11.76471% with 15 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (develop@f4eda5a). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
fastdeploy/model_executor/models/deepseek_v3.py	0.00%	13 Missing ⚠️
fastdeploy/model_executor/layers/linear.py	50.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             develop    #8083   +/-   ##
==========================================
  Coverage           ?   67.55%           
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  Files              ?      475           
  Lines              ?    66912           
  Branches           ?    10320           
==========================================
  Hits               ?    45204           
  Misses             ?    18833           
  Partials           ?     2875           

Flag	Coverage Δ
GPU	77.58% <11.76%> (?)
XPU	6.95% <0.00%> (?)

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[PaddlePaddle-bot]

🤖 Paddle-CI-Agent | ci_status_monitor | 2026-06-29 18:00:44 UTC+08:00

CI报告基于以下代码生成（30分钟更新一次）:
PR commit: 97c30e5 | Merge base: f4eda5a (branch: develop)

---

1 Required任务 : 9/10 通过

总执行（rerun次数）	总任务	✅ 通过	❌ 失败	⏳ 运行中	⏸️ 等待中	跳过
113(72)	41	37	4	0	0	0

任务	错误类型	置信度	日志
Run FastDeploy Unit Tests and Coverage / run_tests_with_coverage	PR问题：增量覆盖率仅 11%，未达 80%	高	Job

2 失败详情

🔴 Run FastDeploy Unit Tests and Coverage / run_tests_with_coverage — PR问题（置信度: 高）

分析器: 通用分析(fallback)

失败用例: 覆盖率阈值校验

用例	错误摘要
Verify Code Coverage Threshold (80%)	增量覆盖率 11%，低于 80% 阈值，步骤以 exit code 9 失败

关键日志:

TEST_EXIT_CODE=0
COVERAGE_EXIT_CODE=9
Verify Code Coverage Threshold (80%)
total_num_lines=17, total_num_violations=15, total_percent_covered=11
violations: fastdeploy/model_executor/layers/linear.py:1142, 1154
Process completed with exit code 9.

• 根因摘要: 新增 KVBatchLinear helper 未补充单测

PR 新增 KVBatchLinear.forward_k_b_thd() 和 forward_v_b_htr()，并在 DeepSeek V3 注意力路径中改用这两个 helper。CI 单测阶段已通过，但覆盖率校验显示本次变更的 17 个有效覆盖行中有 15 行未覆盖，整体增量覆盖率只有 11%，其中 linear.py:1142、linear.py:1154 是两个新增 einsum 返回逻辑。现有 tests/model_executor/test_linear.py::test_kvbatch_paths 只调用旧的 forward_k_b() / forward_v_b()，没有覆盖新增 THD/HTR 布局 helper。

修复建议:

1. 在 tests/model_executor/test_linear.py::test_kvbatch_paths 中增加 forward_k_b_thd() 和 forward_v_b_htr() 的断言，覆盖输出 shape 和数值等价性。
2. 建议用同一组权重对比旧路径：forward_k_b(x.transpose([1, 0, 2])).transpose([1, 0, 2]) 与 forward_k_b_thd(x)，以及 forward_v_b(x.transpose([1, 0, 2])).transpose([1, 0, 2]) 与 forward_v_b_htr(x)。
3. 如 DeepSeek V3 改动还触发未覆盖分支，补充对应 attention forward 路径测试或拆出可单测的投影逻辑。

关联变更: fastdeploy/model_executor/layers/linear.py:1132, fastdeploy/model_executor/layers/linear.py:1144, fastdeploy/model_executor/models/deepseek_v3.py:457, fastdeploy/model_executor/models/deepseek_v3.py:622, fastdeploy/model_executor/models/deepseek_v3.py:1027