---
id: pr-vllm-38361
repo: vllm-project/vllm
pr: 38361
title: '[GDN] Eliminate GPU->CPU sync in prepare_chunk_indices during prefill'
author: arpera
date: '2026-04-03'
url: https://github.com/vllm-project/vllm/pull/38361
source_category: upstream-code
architectures:
- sm100
tags:
- attention
- prefill
techniques: []
hardware_features: []
kernel_types:
- attention
- prefill
languages:
- python
captured_at: '2026-04-17'
status: merged
merge_sha: cb10b7e80b138f876079c2cd697df29f0965b885
inclusion_reason: kernel file changes
changed_paths:
- vllm/model_executor/layers/fla/ops/chunk.py
- vllm/model_executor/layers/fla/ops/chunk_delta_h.py
- vllm/model_executor/layers/fla/ops/chunk_o.py
- vllm/model_executor/layers/fla/ops/chunk_scaled_dot_kkt.py
- vllm/model_executor/layers/fla/ops/cumsum.py
- vllm/model_executor/layers/fla/ops/kda.py
- vllm/model_executor/layers/fla/ops/solve_tril.py
- vllm/model_executor/layers/fla/ops/wy_fast.py
- vllm/model_executor/layers/mamba/gdn_linear_attn.py
- vllm/v1/attention/backends/gdn_attn.py
head_ref_oid: 1a86ef615bae9b8cd422be8dde67c68b1ce12d7c
artifact_dir: evidence/pull-bundles/vllm/gh-38361
---
# [GDN] Eliminate GPU->CPU sync in prepare_chunk_indices during prefill

- Repository: `vllm-project/vllm`
- PR: [38361](https://github.com/vllm-project/vllm/pull/38361)
- Decision: `kernel file changes`
- Reason: kernel file changes

## Changed Paths

- `vllm/model_executor/layers/fla/ops/chunk.py`
- `vllm/model_executor/layers/fla/ops/chunk_delta_h.py`
- `vllm/model_executor/layers/fla/ops/chunk_o.py`
- `vllm/model_executor/layers/fla/ops/chunk_scaled_dot_kkt.py`
- `vllm/model_executor/layers/fla/ops/cumsum.py`
- `vllm/model_executor/layers/fla/ops/kda.py`
- `vllm/model_executor/layers/fla/ops/solve_tril.py`
- `vllm/model_executor/layers/fla/ops/wy_fast.py`
- `vllm/model_executor/layers/mamba/gdn_linear_attn.py`
- `vllm/v1/attention/backends/gdn_attn.py`

## Evidence Bundle

`evidence/pull-bundles/vllm/gh-38361`
