---
id: pr-vllm-34043
repo: vllm-project/vllm
pr: 34043
title: Reapply [Attention][FA3] Update FA3 to include new swizzle optimization
author: LucasWilkinson
date: '2026-02-11'
url: https://github.com/vllm-project/vllm/pull/34043
source_category: upstream-code
architectures:
- sm90
tags:
- attention_kv
- hopper
techniques:
- swizzling
hardware_features:
- hopper
kernel_types:
- attention
- mla
languages:
- cuda-cpp
captured_at: '2026-05-16'
status: merged
merge_sha: c7914d30f90bc47f1c959d3330666885a0034f7d
inclusion_reason: Preserve page/KV/layout and plan-run contracts; profile memory traffic separately from math utilization.
changed_paths:
- cmake/external_projects/vllm_flash_attn.cmake
- tests/v1/cudagraph/test_cudagraph_dispatch.py
- vllm/forward_context.py
- vllm/v1/attention/backends/flash_attn.py
- vllm/v1/attention/backends/mla/flashattn_mla.py
- vllm/v1/cudagraph_dispatcher.py
artifact_dir: evidence/pull-bundles/vllm/gh-34043
head_ref_oid: 695c06b4d90e431b58b2332ab5752c885a2a064c
---
# Reapply [Attention][FA3] Update FA3 to include new swizzle optimization

- Repository: `vllm-project/vllm`
- PR: [34043](https://github.com/vllm-project/vllm/pull/34043)
- 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

- `cmake/external_projects/vllm_flash_attn.cmake`
- `tests/v1/cudagraph/test_cudagraph_dispatch.py`
- `vllm/forward_context.py`
- `vllm/v1/attention/backends/flash_attn.py`
- `vllm/v1/attention/backends/mla/flashattn_mla.py`
- `vllm/v1/cudagraph_dispatcher.py`

## Evidence Bundle

`evidence/pull-bundles/vllm/gh-34043`
