---
id: pr-vllm-25954
repo: vllm-project/vllm
pr: 25954
title: '[Performance] Split FlashAttn attention and cache update'
author: ElizaWszola
date: '2026-01-24'
url: https://github.com/vllm-project/vllm/pull/25954
source_category: upstream-code
architectures:
- sm100
tags:
- attention
- decode
techniques: []
hardware_features: []
kernel_types:
- attention
- decode
languages:
- cuda-cpp
captured_at: '2026-04-27'
status: merged
merge_sha: a28b94e6ef60b7f5aa1b97bc8d966a8d12cbc1da
inclusion_reason: kernel file changes
changed_paths:
- tests/v1/attention/test_attention_backends.py
- tests/v1/attention/utils.py
- tests/v1/kv_connector/unit/test_decode_bench_connector.py
- tests/v1/kv_connector/unit/test_nixl_connector.py
- tests/v1/kv_connector/unit/test_offloading_connector.py
- tests/v1/spec_decode/test_tree_attention.py
- vllm/attention/layer.py
- vllm/forward_context.py
- vllm/model_executor/layers/attention/cross_attention.py
- vllm/utils/torch_utils.py
- vllm/v1/attention/backend.py
- vllm/v1/attention/backends/flash_attn.py
- vllm/v1/spec_decode/eagle.py
- vllm/v1/spec_decode/medusa.py
- vllm/v1/spec_decode/ngram_proposer.py
- vllm/v1/spec_decode/suffix_decoding.py
- vllm/v1/worker/gpu/attn_utils.py
- vllm/v1/worker/gpu/cudagraph_utils.py
- vllm/v1/worker/gpu/model_runner.py
- vllm/v1/worker/gpu_model_runner.py
- vllm/v1/worker/gpu_ubatch_wrapper.py
head_ref_oid: 5c0247f155ce1e761732e94c90800d23bc6ad4b1
artifact_dir: evidence/pull-bundles/vllm/gh-25954
---
# [Performance] Split FlashAttn attention and cache update

- Repository: `vllm-project/vllm`
- PR: [25954](https://github.com/vllm-project/vllm/pull/25954)
- Decision: `kernel file changes`
- Reason: kernel file changes

## Changed Paths

- `tests/v1/attention/test_attention_backends.py`
- `tests/v1/attention/utils.py`
- `tests/v1/kv_connector/unit/test_decode_bench_connector.py`
- `tests/v1/kv_connector/unit/test_nixl_connector.py`
- `tests/v1/kv_connector/unit/test_offloading_connector.py`
- `tests/v1/spec_decode/test_tree_attention.py`
- `vllm/attention/layer.py`
- `vllm/forward_context.py`
- `vllm/model_executor/layers/attention/cross_attention.py`
- `vllm/utils/torch_utils.py`
- `vllm/v1/attention/backend.py`
- `vllm/v1/attention/backends/flash_attn.py`
- `vllm/v1/spec_decode/eagle.py`
- `vllm/v1/spec_decode/medusa.py`
- `vllm/v1/spec_decode/ngram_proposer.py`
- `vllm/v1/spec_decode/suffix_decoding.py`
- `vllm/v1/worker/gpu/attn_utils.py`
- `vllm/v1/worker/gpu/cudagraph_utils.py`
- `vllm/v1/worker/gpu/model_runner.py`
- `vllm/v1/worker/gpu_model_runner.py`
- `vllm/v1/worker/gpu_ubatch_wrapper.py`

## Evidence Bundle

`evidence/pull-bundles/vllm/gh-25954`
