---
id: pr-vllm-40392
repo: vllm-project/vllm
pr: 40392
title: '[Performance][DSR1]: Fused RoPE+KVCache+q_concat for MLA'
author: Rohan138
date: '2026-05-11'
url: https://github.com/vllm-project/vllm/pull/40392
source_category: upstream-code
architectures:
- sm100
tags:
- attention_kv
- benchmark_test
- memory_primitives
- mxfp4
techniques:
- cache-policy
- kernel-fusion
hardware_features:
- fp4
- mxfp4
kernel_types:
- attention
- memory
- mla
languages:
- cuda-cpp
captured_at: '2026-05-16'
status: merged
merge_sha: a51376b3f05a2f74eac6ceeed7e52598b871a0fb
inclusion_reason: Preserve page/KV/layout and plan-run contracts; profile memory traffic separately from math utilization.
changed_paths:
- csrc/cache_kernels_fused.cu
- tests/compile/passes/test_mla_rope_kvcache_cat_fusion.py
- tests/compile/passes/test_rope_kvcache_fusion.py
- vllm/compilation/passes/fusion/matcher_utils.py
- vllm/compilation/passes/fusion/mla_rope_kvcache_cat_fusion.py
- vllm/compilation/passes/pass_manager.py
- vllm/compilation/passes/utility/fix_functionalization.py
- vllm/config/compilation.py
- vllm/config/vllm.py
- vllm/model_executor/layers/attention/mla_attention.py
- vllm/model_executor/layers/rotary_embedding/deepseek_scaling_rope.py
- vllm/model_executor/layers/rotary_embedding/dual_chunk_rope.py
artifact_dir: evidence/pull-bundles/vllm/gh-40392
head_ref_oid: 287b221c90b48bd66e1d7fdd7ba6fe4db55cb8fd
---
# [Performance][DSR1]: Fused RoPE+KVCache+q_concat for MLA

- Repository: `vllm-project/vllm`
- PR: [40392](https://github.com/vllm-project/vllm/pull/40392)
- Decision: `Preserve page/KV/layout and plan-run contracts; profile memory traffic separately from math utilization.`
- Reason: Preserve page/KV/layout and plan-run contracts; profile memory traffic separately from math utilization.

## Changed Paths

- `csrc/cache_kernels_fused.cu`
- `tests/compile/passes/test_mla_rope_kvcache_cat_fusion.py`
- `tests/compile/passes/test_rope_kvcache_fusion.py`
- `vllm/compilation/passes/fusion/matcher_utils.py`
- `vllm/compilation/passes/fusion/mla_rope_kvcache_cat_fusion.py`
- `vllm/compilation/passes/pass_manager.py`
- `vllm/compilation/passes/utility/fix_functionalization.py`
- `vllm/config/compilation.py`
- `vllm/config/vllm.py`
- `vllm/model_executor/layers/attention/mla_attention.py`
- `vllm/model_executor/layers/rotary_embedding/deepseek_scaling_rope.py`
- `vllm/model_executor/layers/rotary_embedding/dual_chunk_rope.py`

## Evidence Bundle

`evidence/pull-bundles/vllm/gh-40392`
