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Merged
merged 121 commits into from
Nov 11, 2025
Merged

[Attention] Refactor CUDA attention backend selection logic #24794

merged 121 commits into from
Nov 11, 2025

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@MatthewBonanni
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@MatthewBonanni MatthewBonanni commented Sep 13, 2025 •
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Purpose

CudaPlatformBase.get_attention_backend_cls has gotten complex and messy over time. This PR cleans up the logic (without changing the behavior) and standardizes the interface.

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Essential Elements of an Effective PR Description Checklist
  • The purpose of the PR, such as "Fix some issue (link existing issues this PR will resolve)".
  • The test plan, such as providing test command.
  • The test results, such as pasting the results comparison before and after, or e2e results
  • (Optional) The necessary documentation update, such as updating supported_models.md and examples for a new model.
  • (Optional) Release notes update. If your change is user facing, please update the release notes draft in the Google Doc.

@mergify mergify bot added rocm Related to AMD ROCm speculative-decoding v1 tpu Related to Google TPUs labels Sep 13, 2025
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mergify bot commented Sep 13, 2025

This pull request has merge conflicts that must be resolved before it can be
merged. Please rebase the PR, @MatthewBonanni.

https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/working-with-forks/syncing-a-fork

@mergify mergify bot added the needs-rebase label Sep 13, 2025
njhill
njhill reviewed Sep 13, 2025
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@MatthewBonanni MatthewBonanni changed the title [Attention] Refactor CUDA attention backend selection logic [WIP][Attention] Refactor CUDA attention backend selection logic Sep 13, 2025
@MatthewBonanni MatthewBonanni changed the title [WIP][Attention] Refactor CUDA attention backend selection logic [Attention] Refactor CUDA attention backend selection logic Sep 16, 2025
@MatthewBonanni MatthewBonanni marked this pull request as ready for review September 16, 2025 13:22
@mergify mergify bot removed the needs-rebase label Sep 16, 2025
@LucasWilkinson LucasWilkinson mentioned this pull request Nov 10, 2025
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LucasWilkinson commented Nov 10, 2025

@MatthewBonanni how hard would it be to keep backwards compatibility between _Backend and AttentionBackendEnum for a version with a warning?

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LucasWilkinson commented Nov 10, 2025

With #26487 potential in the pipe what do we think about having a get_mla_attn_backend_cls instead of is_mla? @Yikun ?

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MatthewBonanni commented Nov 10, 2025

@MatthewBonanni how hard would it be to keep backwards compatibility between _Backend and AttentionBackendEnum for a version with a warning?

@LucasWilkinson done in d0f4698

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NickLucche commented Nov 10, 2025

Discussed offline thanks for the work @MatthewBonanni !

wangxiyuan
wangxiyuan approved these changes Nov 11, 2025
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vllm/attention/backends/registry.py
return AttentionBackendEnum[name]


class _Backend(metaclass=_BackendMeta):
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Nice change

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mgoin
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Release has been cut, let's go for it on main

@github-project-automation github-project-automation bot moved this to Ready in NVIDIA Nov 11, 2025
@mgoin mgoin merged commit b30dfa0 into vllm-project:main Nov 11, 2025
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@github-project-automation github-project-automation bot moved this from Ready to Done in NVIDIA Nov 11, 2025
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hmellor commented Nov 11, 2025

The merge commit of this PR failed pre-commit because the base of the branch was out of date

@MatthewBonanni MatthewBonanni deleted the backend_selection_refactor branch November 11, 2025 14:29
@MatthewBonanni MatthewBonanni mentioned this pull request Nov 11, 2025
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@hl475 hl475 mentioned this pull request Nov 12, 2025
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@njhill njhill mentioned this pull request Nov 12, 2025
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xuebwang-amd pushed a commit to xuebwang-amd/vllm that referenced this pull request Nov 13, 2025
@MatthewBonanni @ProExpertProg @xuebwang-amd
[Attention] Refactor CUDA attention backend selection logic (vllm-pro…
9ac7938 
…ject#24794)

Signed-off-by: Matthew Bonanni <[email protected]>
Signed-off-by: Matthew Bonanni <[email protected]>
Co-authored-by: Luka Govedič <[email protected]>
Signed-off-by: xuebwang-amd <[email protected]>
@MatthewBonanni MatthewBonanni mentioned this pull request Nov 13, 2025
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leo-pony added a commit to 22dimensions/vllm-ascend that referenced this pull request Nov 19, 2025
@leo-pony
vllm break of PR:vllm-project/vllm#24794
111f445 
Signed-off-by: leo-pony <[email protected]>
@NickLucche NickLucche mentioned this pull request Nov 20, 2025
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wangxiyuan pushed a commit to wangxiyuan/vllm-ascend that referenced this pull request Nov 24, 2025
@leo-pony @wangxiyuan
vllm break of PR:vllm-project/vllm#24794
1fe271a 
Signed-off-by: leo-pony <[email protected]>
wangxiyuan pushed a commit to wangxiyuan/vllm-ascend that referenced this pull request Nov 24, 2025
@leo-pony @wangxiyuan
vllm break of PR:vllm-project/vllm#24794
58303c8 
Signed-off-by: leo-pony <[email protected]>
devpatelio pushed a commit to SumanthRH/vllm that referenced this pull request Nov 29, 2025
@MatthewBonanni @ProExpertProg @devpatelio
[Attention] Refactor CUDA attention backend selection logic (vllm-pro…
eea77ba 
…ject#24794)

Signed-off-by: Matthew Bonanni <[email protected]>
Signed-off-by: Matthew Bonanni <[email protected]>
Co-authored-by: Luka Govedič <[email protected]>
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ci/build deepseek Related to DeepSeek models documentation Improvements or additions to documentation frontend gpt-oss Related to GPT-OSS models kv-connector multi-modality Related to multi-modality (#4194) new-model Requests to new models nvidia performance Performance-related issues qwen Related to Qwen models ready ONLY add when PR is ready to merge/full CI is needed rocm Related to AMD ROCm speculative-decoding structured-output tpu Related to Google TPUs v1

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@MatthewBonanni @ILikeIneine @mgoin @LucasWilkinson @NickLucche @hmellor @wangxiyuan @ProExpertProg @njhill